1. Report type: Research Report
Author: Bachelor of Water Management –Year 4
Course: River Basin Management
Date of publication: September 2013
Location: Cadiz, Spain
Version number: 2.0
System Analysis of the Guadalete River Basin
Ecological system assessment of the river and its environment
2. II
System Analysis of the Guadalete River Basin
Ecological system assessment of the river and its environment
What is the State of Guadalete River Basin?
This state is defined by the chemical, biological, hydrological and geomorphological
properties of the river basin, as well as the involvement and influence of
stakeholders
Report type: Research Report
Author: Bachelor of Water Management –Year 4
Course: River Basin Management
Date of publication: September 2013
Location: Region of Cadiz, Spain
Version number: 2.0
3. III
Preface
The EU IP (intensive programmes) project RAMIP (River Delta System Analysis and
Management in Practice) has brought 48 students and 15 staffs together from 4
different universities to learn from each other various environment and risk
disciplines aiming to integrate them in a specific field case study and apply these
techniques and concepts for the river system analysis and management plans. The
studies are done from biological, chemical, hydrological, geomorphological aspects
that assess, discuss and analyze the situation of Guadalete River. The stakeholders
from the river basin are interviewed for further information. The field week and
analysis was conducted from Saturday 14/9 – Friday 20/9. In this report the results
of the first week are presented and analyzed. In the second week the focus lies on
vision and scenario building and measures to improve the actual state of the
Guadalete River basin.
The students and staff of four different Universities are responsible for the project:
HZ University of Applied Sciences (The Netherlands), Helsinki Metropolia University
of Applied Sciences (Finland), Ferrara University (Italy) and Cadiz University
(Spain). The project is made possible by the financial contribution of the EU Lifelong
Learning Programs
4. IV
Summary
A water system analysis was conducted in the Guadalete River Basin where the
aspects of geomorphology, hydrology, chemistry and biology are taken into
consideration.
The geomorphological state of the river basin was assessed using IDRIAM system
where the MQI is determined for each sampling spot. 50% of the MQI values were
excellent. The geomorphologic state of the entire river basin is good with only poor
areas where manmade structures are situated. The global slope of the river basin is
0.0056 for the upper river basin, 0.0019 for the middle and 0.0006 for the lower
river basin.
The hydrological assessment was conducted using two method; the OTT Qliner
ultrasonic current profiler downstream and measuring line, pole and "flipper"
upstream. The flow rate gradually increases from 5.3 m3/L at the Zahara outflow to
6 m3/L at the Bornos reservoir inflow. The dams regulate the water flow. After the
Arcos dam the flow rate was 5.9 m3/L and gradually increases again to 11.3 m3/L at
El Torno. A Sobek model was built. The hydrology of the Guadalete is entirely
controlled through human engineering and is therefore an anthropologic system.
The chemical assessment was conducting along the river course with in field
measurements and laboratory analysis. The Hach-Lange spectrophotometer was
used for the chemical analysis. The oxygen concentrations, pH levels were stable.
The total nitrogen level only exceeded the EU standard for surface water (2.2 mg/L)
after the WWTP of Jerez with a value of 8.29 mg/L. The total phosphorus level
exceeded the EU standard for surface water (0.15 mg/L) at several sampling points.
The highest being Villamartín with 0.486 mg/L and 0.345 mg/L after the WWTP of
Jerez. The effluent water of the WWTP also exceeded the EU standards for effluent
water for total phosphorus (1.0 mg/L) and total nitrogen (10 mg/L) with total
phosphorus concentration of 1.5 mg/L and total nitrogen level of 46.60 mg/L. The
Bornos Lake was stratified with no Oxygen at the bottom at the sampling point. The
overall chemical state of the river is good with only point pollutions at Villamartín
and especially after the WWTP of Jerez.
The biological assessment was conducted using the saprobic index and biotic index.
The biological state progressively decreases heading downstream, particularly after
the WWTP of Jerez. Macrophytes indicate that the river is a nutrient and carbon rich
environment. Certain macrophytes species discovered at three different locations
indicate a nutrient poor environment.
In addition, the stakeholders of the river basin were interviewed. Communication
between stakeholders is poor and conflicts are common. Lack of community
awareness increases pollution and illegal landfills were found. The attitude towards
the river is negative and law enforcement is low.
5. V
Table of Abbreviations
EU IP European Intensive Program
IDRIAM Stream hydro-morphological evaluation,
analysis and monitoring system
DGPS Differential Global Positioning System
GPS Global Positioning System
SW South West
MQI Morphological Quality Index
MAI
d50,85 Discharge at 50%, 84%
v Steady flow velocity
Q Flow rate
Qbd Flow rate of bank full discharge
A Surface area
Abd Area of bank full discharge
SOBEK Software program for hydraulic
modelling
OTT Qliner Instrument for hydraulic measurments
WWTP Waste water treatment plant
6. VI
List of Authors
Barbara Ansaloni / Francesco Cassari Francesco / Enrico Duo / Tommaso Furlani /
Serena Miazzi / Alessandra Casari / Dorella Maruccia
Anna Vasileva / Olga Gerasimenko / Eila Jenny Anneli Mylllylä / Bhawani Regmi /
Sanchit Bista / Bipin Dulal
María Rocio Ramos / Maria Aranda Garcia / Alexandre Martinez Schonemann /
Laura Cadiz Berrera / Pablo Matin Binder / Gozalbes Carlos Garcia
Lieke Beezemer / Eric Martinus Bisslik / Rebecca Naomi ter Borg / René
Bouwmeester / Dirk Theodoor Henricus Bremmers / Rita Sofia Cardoso Vaina de
Lemos / Tianyi Hu / Maarten Fritz / Godfried Gijsbert franciscus Kersten / Niek
Wouter Koelen / Jevgenijs Kuzmins / Iris van der Laan / Joshi Lenferink / Arthur
Ricardo van Pampus / Jelle Pieters / Gerardus Cornelis Nicolaas van der Pluijm /
Laura Schneegans / Johannes Schoordijk / Martin Stefan Skaznik / Maria Orhideea
Tatar / Forrest Tyler van Uchelen / Artis Vansovics / David Verschoor / Mengxiao
Wang / Rudolf Wilhelmus Johannes Weterings / Marco Wiemer / Jerre Binne Doeke
Wiersma / Nadine Maria Willems / Tianwen Xia
7. VII
List of Figures
Figure 1: Gaudalete River Basin ______________________________________________________________________________ 4
Figure 2: Elevation Measurements __________________________________________________________________________11
Figure 5: Metal gran size determinator _____________________________________________________________________12
Figure 6: Different grain sizes sorted by phi ________________________________________________________________13
Figure 7: Sieves in different grain sizes______________________________________________________________________13
Figure 8: Hjulstrom graph (http://dlgb.files.wordpress.com/2008/09/hjulstrom_curve_task.jpg )_____16
Figure 9: Layout of the sampling points aong the Guadalete river ________________________________________25
Figure 10: OTT QLiner method.______________________________________________________________________________26
Figure 11: Illutration of the Qliner method measurement _________________________________________________27
Figure 12: Example cross-section including wet and dry section. Of point 20_____________________________28
Figure 13: Side view of the SOBEK model ___________________________________________________________________31
Figure 14: Influence of the tidal weir________________________________________________________________________31
Figure 15: Velocity at point 110 _____________________________________________________________________________32
Figure 16: Velocity at point 120 _____________________________________________________________________________33
Figure 17: Precipitation map Rio Guadalete River Basin (Source: Presentation Javier Gracia). _________34
Figure 18: Main aquifers in the Guadalete River Basin (Source: Presentation Javier Gracia). ___________35
Figure 19: Map of the sampling points from the inlet of Zahara till Puerto de Santa Maria._____________39
Figure 20: Biological assessments provide information on the cumulative effects on aquatic
communities from multiple stressors. (USEPA, 2003).______________________________________________________51
Figure 21: Main feedback relations within the ecosystem structure. (Adapted from Scheffer et al, 1993)
________________________________________________________________________________________________________________52
Figure 22: Map showing the location of sampling points. __________________________________________________54
Figure 23: Identification of the Sampling area in each of the sampling points. ___________________________57
Figure 24: Graphical representation of the Saprobic Index results along the River Guadalete. Color Legend:
Green: β-mesosaprobic; Yellow: α-mesosaprobic. __________________________________________________________60
Figure 25: Example of two poor nutrient environment indicators found during the fieldwork. Right
panel: Lithospermum officinale. Left panel: Montia fontana_______________________________________________61
Figure 26: Result map after applying the Biotic Index in sampling points.________________________________67
Figure 27: Macroinvertebrates found in the Guadalete basin. a) Ecdyonurus; b) Physella acuta; c)
Hydropsychidae; d) Procambarus clarki. ___________________________________________________________________68
Figure 28: Land use of the Guadalete river basin region with the river highlighted in blue______________75
Figure 29: Cause and effect diagram ________________________________________________________________________85
Figure 30: DPSIR Analysis____________________________________________________________________________________87
8. VIII
List of Graphs
Graph 1: Morphological quality index of the Guadalete river ______________________________________________14
Graph 2: Grain size distribution _____________________________________________________________________________16
Graph 3: Velocity and grain size comparaison______________________________________________________________17
Graph 4: Point 10 – Cross Section ___________________________________________________________________________18
Graph 5: Point 20 – Cross Section ___________________________________________________________________________18
Graph 6: Point 30 – Cross Section ___________________________________________________________________________19
Graph 7: Point 60 – Cross Section ___________________________________________________________________________19
Graph 8: Point 80 – Cross Section ___________________________________________________________________________20
Graph 9: Banfull Discharge of the Guadalete river _________________________________________________________21
Graph 10: Global Slope of the Guadalete river ______________________________________________________________21
Graph 11: Elevation of the Guadalete river _________________________________________________________________22
Graph 12: Local slope of the Guadalete river basin_________________________________________________________22
Graph 13: measured velocities and calculated flow rates __________________________________________________30
Graph 14: Oxygen Concentration ____________________________________________________________________________42
Graph 15: pH of the Guadalete river_________________________________________________________________________43
Graph 16: Conductivity of the Guadalete river______________________________________________________________44
Graph 17: Nitrogen levels in the Guadalete river ___________________________________________________________45
Graph 19: Stratification of the temperature in Bornos reservoir __________________________________________47
Graph 20: Stratification of the oxygen in Bornos reservoir ________________________________________________47
Graph 21: Stratification of the pH in Bornos reservoir _____________________________________________________48
List of Tables
Table 1: Morphological Quality Index classes_______________________________________________________________10
Table 2: Overview of the quality class appointed, by using the IDRIAM form _____________________________14
Table 3: Overview of the measurement points ______________________________________________________________15
Table 4: Measured velocities and calculated flow rates ____________________________________________________29
Table 5: Main aquifers in the Guadalete River Basin (Source: Lopez Geta, 2005)_________________________35
Table 6: table of the sampling points from the inlet of Zahara till Puerto de Santa Maria. ______________40
Table 7: Codification of sampling points and a short description__________________________________________54
Table 8: Grades assigned to different taxa according to its presence-absence in the water-body.
(Extracted from De Pauw and Vannevel, 1991) ____________________________________________________________56
Table 9: Biochemical values used to classify the systems. Derived from Hamm (1969), Lange-Bertalot
(1978, 1979) and Krammer and Lange-Bertalot (1986-1991) ____________________________________________59
Table 10: Macrophyte species found on each sampling point. First two rows shows geographic
coordinates and sample point code respectively. ___________________________________________________________62
Table 11: Environmental needs for different macrophyte found in the sampling points._________________64
Table 12: Detail of the taxa found on sampling point 20. __________________________________________________66
Table 13: Detail of the taxa found on sampling point 90. __________________________________________________67
Table 14: Family list of macroinvertebrates found in the river Guadalete ________________________________69
Table 15: Comparison between Ebro occurring species and the ones found in the Guadalete River
autochthonous and invasive species. (Extracted from Oscoz, 2009) _______________________________________70
Table 16: Stakeholders and their water use ________________________________________________________________77
Table 17: Influence of individual stakeholders, - 1 = very low / 2 = low / 3 = medium / 4 = high / 5 = very
high ___________________________________________________________________________________________________________80
Table 18: Ecological issues concerning the Guadalete river basin _________________________________________89
9. 9
Table of Contents
Preface........................................................................................................................................III
Summary.................................................................................................................................... IV
Table of Abbreviations ...........................................................................................................V
List of Authors.......................................................................................................................... VI
List of Figures..........................................................................................................................VII
List of Graphs ........................................................................................................................VIII
List of Tables .........................................................................................................................VIII
1. Introduction...........................................................................................................................1
1.1 Background................................................................................................................................1
1.2 Assignment.................................................................................................................................2
1.2.1 Aim & Goals ...........................................................................................................................................2
1.2.2 Research Questions:...........................................................................................................................3
2. Research Design ...................................................................................................................4
2.1 Area ..................................................................................................................................................4
2.2 Organizations:...............................................................................................................................5
2.3 Fields of Interest..........................................................................................................................5
2.3.1 Geomorphology ...................................................................................................................................5
2.3.2 Hydrology...............................................................................................................................................6
2.3.3 Chemistry...............................................................................................................................................7
2.3.4 Biology.....................................................................................................................................................8
2.3.5 Stakeholders..........................................................................................................................................8
4. Geomorphology ....................................................................................................................9
4.1. Aim and research questions...................................................................................................9
4.2 Materials.........................................................................................................................................9
4.3 Methods........................................................................................................................................ 10
4.3.1 IDRIAM evaluation forms .............................................................................................................10
4.3.2 Cross sections....................................................................................................................................10
4.3.3 Slopes....................................................................................................................................................11
4.3.4 Sediments............................................................................................................................................12
4.4 Results and Discussions......................................................................................................... 13
4.4.1 IDRIAM evaluation forms .............................................................................................................13
4.4.2 Sediment samples............................................................................................................................14
4.4.3 Cross-sections....................................................................................................................................18
4.4.5 Bank full discharge..........................................................................................................................20
4.4.6 Slope......................................................................................................................................................21
4.4.7 General discussion...........................................................................................................................22
4.5 Conclusion................................................................................................................................... 24
5. Hydrology ............................................................................................................................ 25
11. 11
8.5 Conflict and Problems............................................................................................................. 89
8.6 Conclusion................................................................................................................................... 93
9. Discussion............................................................................................................................ 94
10. Conclusion......................................................................................................................... 99
11. Reference list .................................................................................................................100
12. Appendix..........................................................................................................................103
Appendix I: IDRIAM form............................................................................................................103
Appendix II: Grain size distribution .......................................................................................110
Appendix III: Slope values..........................................................................................................112
Appendix IV: Grain size classificatio.......................................................................................113
Appendix V: Materials Chemistry ............................................................................................114
Appendix VI:Complete lists of macroinvetebrate found on each sampling point..115
Appendix VII: Interview water purification plant .............................................................122
Appendix VIII: Waste Water Treatment Plant ....................................................................123
Appendix IX: Interview about tourism and coastal management................................125
Appendix X: Interview Ecology action group.......................................................................127
Appendix XI: Interview................................................................................................................129
1st Speaker Environmental Department......................................................................................... 129
2nd Speaker Surface and Ground water Quality Department................................................. 130
3rd Speaker Regional Government Department of Land Use ................................................. 132
12. 1
1. Introduction
1.1 Background
The Guadalete River is a river in Spain, located in the region of Andalucía and
originates from the ‘Sierra de la Grazalema’ at the height of 1000 meters above the sea
level and highest peak of 1600 meters above sea level. The river has a total length of
172 km and flows into the Atlantic Ocean at the bay of Cadiz on the Puerto de Santa
Maria where it discharges about 600 hm3
per year. Along the course of the river there
are three reservoirs; Zahara reservoir, Bornos reservoir and Arcos de la Frontera
reservoir. The last 16 kilometres of the river is an estuary influenced by oceanic tides
which are obstructed by a weir at El Portal. Agriculture is practiced in the majority of
the mid-lower river basin and there are also natural protected areas around the
Grazalema mountain range where the Zahara reservoir is located and at the estuary
near the coast close to Puerto de Santa Maria (Javier Garcia presentation).
The climate is moderately subtropical with dry summers and mild winters. The
influence of the sea affects the area’s weather, avoiding extreme temperatures and
with soft oscillations between winter and summer. However, the summer has a
relatively high temperature and low precipitation in the summer causes the area to
suffer droughts, which results in high uptake of the water for multiple purposes
(www.juntadeandalucia.es 1
). The majority of the precipitation falls on the
mountainous area around Grazalema where clouds are forced upwards and the water
vapour condenses allowing precipitation to take place with an annual precipitation of
about 2000 to 2500 millimetres per year. On the lower part of the river basin there is
significantly lower precipitation with an annual precipitation of about 500 to 700
millimetres a year (Javier Garcia presentation).
During short periods of heavy rainfall, the dry soil can be easily flushed away with
runoff water into the surface water, which might result in an increase in sediments and
higher concentrations of nitrogen from soil fertilizers and the presence of toxins from
pesticides (Deputacion de Granada).
During the summer months the population of the area nearly triples when tourists
show up to enjoy their summer vacation. This sometimes creates water shortages for
those two months. In addition, the increase of the population also creates more
wastewater of such capacity that the waste water treatment plants cannot handle the
amount.
1 http://www.juntadeandalucia.es/temas/medio-ambiente/clima/clima-andalucia.html
13. 2
1.2 Assignment
More and more pressure is put on water systems, especially in delta areas and
estuarine regions. Estuaries are often heavily used by sometimes competing
functions; such as agriculture, navigation, tourism, nature and industry. The
European Water Framework Directive (EWFD) has been set up to make European
Union member states to achieve good qualitative and quantitative status of all
water bodies by 2015.
River Delta System Analysis and Management in Practice (RAMIP) focuses on
multidisciplinary and integrated field survey and workshops and on practical and
theoretical application of the principle of river basin management according to the
EWFD applied in the Spanish Guadalete river delta.
RAMIP’s objective is to facilitate an international, real life and stimulating learning
environment for students. Students and staff of different universities on the one
hand and stakeholders and river basin authorities on the other hand will exchange
experience and knowledge and share ideas leading to a better understanding of the
physical and socio-economic relationships relevant for river basin management.
1.2.1 Aim & Goals
This project was put together for water system analysis of the Guadalete River
Basin. For all communities water is the most valuable resource and managing the
problems takes integration of many different aspects. The state of the Guadalete
River Basin is based on analyzing geomorphology, hydrology, chemistry, biology
and the stakeholders those have impact and are independent on the river. The
current state of the river needs to be analyzed for the problems and also compare
with previous studies.
There are also more goals that are not orientated at methodological problem
solving. The students themselves have to solve problems concerning their
responsibilities, ideas and interest. This goal is to gain experience in working
together in ax social construct towards a solution. The program is described as IP
(intensive project) in two-week time-span. The students collect and analyze data
and create an idea for a future vision of Guadalete River Basin. Students can apply
their theoretical knowledge for actual problem solving and adding up in
experience.
14. 3
1.2.2 Research Questions:
Main Question
What is the State of Guadalete River Basin?
This state is defined by the chemical, biological, hydrological and
geomorphological properties of the river basin, as well as the involvement and
influence of stakeholders
Sub questions
1. What is the geomorphological quality of the Guadalete River basin from
Zahara to Fabrica de Abonos?
2. What is the hydrological situation of the Guadalete River between
Zahara reservoir and El Puerto de Santa Maria?
3. What is the chemical water quality of the Guadalete River between
Zahara reservoir and Puerto de Santa Maria?
4. What is the biological state of the Guadalete River concerning macro-
invertebrates and vegetation and what human activities have an
influence?
5. What is the role of each stakeholder and how do they influence the
Guadalete River basin
15. 4
2. Research Design
2.1 Area
The area of the Guadalete river, see Figure 1, that was investigated for this study
project stretches from the inlet of the Embalse de Zahara-el Gastor to the mouth of
the river at the city of El Puerto de Santa Maria, were after running for about 172
km it enters de Bay of Cádiz.
Figure 1: Gaudalete River Basin
The upstream area of the river lies in an area, which is characterized by hills and
steep slopes, combined with small urban areas and some agricultural land were
they cultivate mainly olives. Downstream the land gradually changes into flatter
areas; hills with agricultural parcels and small cities and villages near the river. At
the end of the river, when it passes Jerez de la Frontera, the land turns even flatter
and here you can find large planes that are mainly used for agriculture and cities.
Finally, the Guadalete river basin enters the Bay of Cádiz were it flows into the
North Atlantic Ocean.
16. 5
2.2 Organizations:
The Guadalete River is investigated by a team of student engineers from 14 till 20
of September 2013, including a field visit of the Guadalete River on 15/9 as well as
a discussion of measurement plan and also analysis and interpretation of the task
on 16/9. During this period of time standardized research methods were used to
extract data.
In total there are 48 students of four different universities. 7 students from Ferrara
University in Italy, 6 students of Metropolian Helsinki in Finland, 6 students of
Cadiz University in Spain and 29 students of Hz University of Applied Sciences in
the Netherlands.
For this investigation it would be logical to use the European Water Framework
Directive (EWFD) as a guideline, it has only partly been adopted here. Moreover,
instead of Spanish assessment methods, Dutch assessment methods have been
applied except for determining the geomorphological quality of the Guadalete
River, which is an Italian method. Moreover, due to a limited period of filed study
time (3 days) and preference for a maximized number of sampling points it would
be more beneficial to investigate only the basic characteristics of the river system
instead of a wide arrange of parameters.
2.3 Fields of Interest
The Guadalete River is investigated according to five different aspects, namely:
stakeholders, geomorphology, hydrology, chemistry and biology. The following
paragraphs introduce the disciplines in terms of aim and motivation. Methods,
results, discussion and conclusion of each discipline can be found in the
subsequent chapters 3, 4, 5 and 6.
2.3.1 Geomorphology
The discipline of geomorphology can be described by the geomorphological quality
of the river. This includes several important factors such as:
Grain size;
Soil type;
Elevation;
Cross sections;
Suspended solids;
GIS maps including data from other groups on the right measurement
locations.
These measurements will be obtained in the field and in the laboratory. Depending
on the location the grain size can be determined in the field or in the laboratory.
Grains (gravel, rocks) bigger than -3.0 phi (8 mm) can be counted and determined
in the field by executing a surface transect, were you take at least 100 samples.
17. 6
Smaller particles should be taken back to the laboratory where they will be sieved
and weighted.
Soil type will be determined based on size (gravel, sand, silt, clay etc.) and
geological maps. The elevation will be measured with a DGPS and by hand; using
jalons (poles), normal GPS and measuring tape. Local slope will be determined in
the field with the help of GIS. The global slope of the river can be calculated in GIS
and with several calculations.
Sediments play an important role in the elemental cycling in aquatic environments.
Most sediment in surface water originates from surface erosion. For the purpose of
aquatic monitoring, sediments can be classified as deposited or suspended.
Deposited sediment can be found on the river bed, suspended sediment can be
found in the water column where it is being transported by water movements.
Many suspended sediments means there is a low visibility and a low visibility will
influence the algae growth and biological activity in and around the river.
Therefore measurements to determine the total suspended solids (TSS) were
conducted.
All data will be put into GIS on the right locations, including some data from the
other disciplines.
2.3.2 Hydrology
This discipline describes the hydraulic and hydrological elements of the river
system in terms of quantitative and qualitative aspect. Important aspects to this
area of research are: flow rate (discharge), flow velocity, flow direction, tidal
influence and the underwater cross sections of the river.
Basic information about flow rate is collected for the Guadalete River and its
tributaries. Such information can be important to resolve question not only related
to hydrology but also geomorphology.
The Guadalete River ends in the bay of Cadiz; therefore we assume there is at least
a part of the river, which is influenced by the tide. It is important to know how far
this tidal influence reaches upstream. Probably this will be till the weir south of El
Portal. To test this hypothesis a measurement of the water lever right after the
weir downstream is performed. The water level is measured every thirty minutes
for a couple of hours. In this way, if there is indeed tidal influence, the water level
will rise or decline. The hypothetical water level rise or decline will be connected
to a rise or decline of the tide in the Bay of Cadiz.
18. 7
2.3.3 Chemistry
This discipline describes the chemical aspects of the Guadalete river system, taking
into account:
Oxygen concentration;
pH;
Conductivity;
Temperature;
N-total;
P-total;
Ammonium;
Nitrate;
Nitrite.
All these factors together present the water quality and the transport of different
substances in the Guadalete River. They will be obtained by field measurements
and laboratory analysis.
Adequate dissolved oxygen is necessary for good water quality. Oxygen is a
necessary element to all forms of life. Natural stream purification processes
require adequate oxygen levels in order to provide for aerobic life forms. As
dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under
stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in large
fish kills.
The pH is a very important indicator for the condition of the water system. The pH
also indicates the presence of carbon dioxide in the water as in most water systems
carbon dioxide and carbonates have a large impact on the pH.
The conductivity is important because this can provide information on the tidal
influence and reach into the river. Some species cannot tolerate high conductivities
and will not live near the estuary region of the river.
Ammonium (NH4+-N), nitrite (NO2—N) and nitrate (NO3—N) can be taken together
as dissolved inorganic nitrogen (DIN) and are important nutrients in the nitrogen
cycle. The nitrogen cycle consists of different important processes like nitrogen
fixation, mineralization, nitrification and denitrification. The measured parameters
are key elements in these processes so they can give a good insight about the
nitrogen conversion into various chemical forms in the aquatic system of the
Guadalete River.
Ortho-phosphate (PO43—P) is an important nutrient because it is often responsible
for eutrophication in ecosystems. Eutrophication means that there are too many
nutrients in the water system; for example through fertilizers, irrigation or WWTP.
This could lead to algae bloom and eventually to oxygen deficit. Because it is often
a key element in fertilizers it can define the relationship between human activity in
the region and ortho-phosphate concentrations found in the Guadalete River.
19. 8
2.3.4 Biology
This discipline describes the biological aspects of the Guadalete River and
surroundings. The emphasis lies on the identification of macro fauna and
macrophyte species living in and around the water. Those species were chosen
because they are sensitive to changes in the aquatic ecosystem and can only live
under certain conditions. Based on the species that were found estimations could
be made about the biological quality of the river.
The data that was gathered can be connected to the other disciplines; such as
chemical-, hydrological- or geological water quality.
In order to perform a multi-habitat measurement sampling of the macro fauna all
the different habitats should be sampled. Furthermore it is very important to take
samples in the right (optimal) time of the year; when flowers are abundant; to get
a proper representation of the present macro fauna. The ideal conditions for
collecting macro fauna samples in a freshwater habitat is once or twice a year. The
samples can be collected from March till October (in order to apply the EWFD).
Samples should be collected in such a way that they represent the whole water
body. Manmade constructions should be avoided, for they might disturb the
sampling location and therefore also the results.
2.3.5 Stakeholders
The discipline describes the impact of stakeholders along the river, taking into
account: policy & legislation, water users (aquaculture, agriculture, industries and
recreation), and wastewater treatment. By means of interviews with stakeholders
and literature research important information is gathered which can be connected
to the other field of interest in this research.
It is important to know the activities of human that live near the Guadalete river
influence the ecological state of the river in terms of hydrology, biology, chemistry
and geomorphology. Straight forward we could say that there is some kind of
influence anyway since humans are part of the ecosystem for thousands of years.
However, the population of the Cadiz region has not always been as high as it is
today, while the Guadalete River and its catchment area and water regime did not
change in such a high rate. Most likely this results in a growing pressure on the
ecological functioning of the river system. Under the discipline of stakeholders as a
part of this study, we aim on identifying the human activities that are expected to
have a major influence on the ecological stat of the Guadalete River.
20. 9
4. Geomorphology
4.1. Aim and research questions
The geomorphology group will investigate the geomorphological quality of the
Guadalete river basin. To determine the geomorphological quality IDRIAM forms
were used. These forms were developed in Italy, where climate, legislation and
river basins are comparable to the ones in South West Spain. In order to complete
on the IDRIAM form several factors should be measured in the field or the
laboratory:
Grain size;
Soil type;
Elevation;
Cross sections;
Bank-full discharge
After all these measurements are carried out the results can be combined with the
results from hydrology, and the hydro-geomorphological state of the Guadalete
river basin can be determined.
The main question that will be answered during this investigation is:
What is the geomorphological situation of the Guadalete river bed from the dam at
Fabrica De Abonos up to Zahara?
4.2 Materials
DGPS device
Total station + tripod
Prism
Carbon pole
Identification poles
Rope
Measuring tape
Grab sampler
Grain size identification
Plastic bags to store sediment samples
Plastic bottle to store water samples
Labels + Pens
Geomorphological survey forms
21. 10
4.3 Methods
4.3.1 IDRIAM evaluation forms
To determine the geomorphological quality of the location an IDRIAM (stream
hydro morphological evaluation, analysis and monitoring system) form was filled in
on each location. This is a questionnaire developed in Italy that gives you a value in
relation to the naturalness of the river. Because Italy and SW Spain have similar
climate, river systems and policies this form can be used. Questions in different
categories have to be answered; namely generality, functionality, artificiality and
channel adjustments.
For each question points can be earned, the more points a river scores the more it
is influences by human construction, industry etc. (so not a natural river). The
quality class is being calculated by subtracting the total points from 1 which leaves
a score from 0 till 1. A quality class explains how much alterations have been
applied to the natural geomorphological state of the river. For example, having a
river in the “poor” quality class means that there were significant changes to the
geomorphological state of the river. To be able to answer all the questions it was
necessary to find out the grain size, length and diameter of the river cross section,
d50 and discharge for example. Therefore, several other measurements need to be
taken in the field.
MQI Quality class
0.0 – 0.3 Very bad
0.3 – 0.5 Poor
0.5 – 0.7 Moderate or sufficient
0.7 – 0.85 Good
0.85 – 1.0 Excellent
Table 1: Morphological Quality Index classes
There are also questions that require historical data or aerial photographs but
since these were not available in such a short period, estimations were made for
these questions. For the form see Appendix I. Based on the results of the
questionnaire, Morphological Quality Index (MQI) was calculated (Error!
Reference source not found.).
4.3.2 Cross sections
Cross sections were measured with either a DGPS or with a total station.
Differential Global Positioning System (DGPS) is an enhancement to Global
Positioning System that provides improved location accuracy, from the 15-meter
nominal GPS accuracy to about 10 cm in case of the best implementations
(M.Braina,2013, C.Kee, 1991).
DGPS uses a network of fixed, ground-based reference stations to broadcast the
difference between the positions indicated by the satellite systems and the known
fixed positions. These stations broadcast the difference between the measured
22. 11
satellite pseudo ranges and actual (internally computed) pseudo ranges, and
receiver stations may correct their pseudo ranges by the same amount. The digital
correction signal is typically broadcast locally over ground-based transmitters of
shorter range.
If possible the transect that was used by the hydrology measurements was
identified. Then the edge of the riverbed was located on both sides and marked
with a pole to make a transect extending upon the hydrology transect (if possible)
to integrate the results later. Along the established transect, elevation
measurements (Figure 2) were taken at points where the vertical angle of the
surface changes. Small features like minor holes or piles were not taken into
account, as they occurred randomly. As a principle, the geomorphology group only
measured the dry part of the riverbed.
Figure 2: Elevation Measurements
When the DGPS was not able to connect with at least five satellites it needs to
correct the signal to within 0.5m accuracy, a total station was used. The measuring
method was the same; only with a total station a clear line of sight without trees or
bushes is necessary from edge to edge so this is not possible on all locations.
The coordinate system used during DGPS survey was UTM ED50 Zone 30N while
for total station a local system has been set (X, Y, Z: 1000m, 1000m, 100m)
4.3.3 Slopes
The local slope at the sampling points was
measured with either a DGPS or a total station.
Along the edge of the water, from roughly 50m
upstream of the transect to 50m downstream of
the transect, the elevation was measured.
For the global slope, the terrain elevation was
measured with the DGPS at sampling point -10
and 20. Other elevation measurements were
taken during the surveys.
Figure 3: Sediment sampling
23. 12
4.3.4 Sediments
The composition of sediments was established in the field using three sampling
methods: Transect Line Method, Areal Sampling and Grab Sampling. The
composition of coarse sediments (> 2.5 phi, see appendix II) was established in the
field. Using a measuring tape stretched along the river bed, the particle right
underneath to the tape was measured every 0.5 m. Using a metal plate with cut
outs (Figure 2) for the rocks in different phi sizes the grain size was determined.
This was repeated several times until at least 100 grain sizes were measured along
the transects, this to obtain a representative sample for the location. The results
were filled out on a form, which can be used to calculate the mean grain size, d50
and soil type (sand, silt, clay or gravel) at the location.
When it was not possible to make a transect line, due to obstructions like trees or
water, a bulk sample was taken. A random squire was chosen, laid out with
measurement tape, and all the surface substrate was taken by hand the taken to
the laboratory. At point 60 the areal sampling method was used to assess the grain
size distribution of coarse surface material sampled in the dry zone of the river’s
cross section in a square surface of 40cmx40cm.This is also representative of the
area. In the laboratory the grain size was determined with the sample plates (see
Figure 4 and Figure 5) and weighted accordingly.
Figure 5: Metal gran size determinator Figure 4: Grain size determinator for small sand
24. 13
Fine sediments were sampled in the field using a grab sampler. The samples were
stored in labeled plastic bags and taken to the field lab. There, the factions were
divided manually using sieves and weighed to establish the d50, mean grain size
and soil type.
Figure 6: Different grain sizes sorted by phi
Figure 7: Sieves in different grain sizes
4.4 Results and Discussions
4.4.1 IDRIAM evaluation forms
Results
By using the IDRIAM evaluation form (see Appendix I: IDRIAM form) each sampling
point could be analyzed and put into a quality class for their current
geomorphological state. Each sampling point could be classed as very bad, poor,
moderate, good or excellent. The results of the research can be found in Table 2.
25. 14
Graph 1: Morphological quality index of the Guadalete river
Measuring point MAI MQI Quality Class
-10 0.06 0.94 Excellent
0 0.03 0.97 Excellent
20 0.40 0.60 Moderate
30 0.22 0.78 Good
40 0.54 0.46 Poor
60 0.52 0.48 Poor
80 0.06 0.94 Excellent
90 0.11 0.89 Excellent
100 0.08 0.92 Excellent
110 0.54 0.46 Poor
Table 2: Overview of the quality class appointed, by using the IDRIAM form
Discussion
As can be seen in the IDRIAM form (see Appendix I: IDRIAM from), there are some
questions that require some historical information of the area. These questions are
related to any alterations of the channel pattern and width since the 1950’s, but
also if there is any sediment, wood or vegetation removal during the last 20 years.
Since this information was not acquired, the grading of these questions has been
done on the assumptions and experience of the supervisor.
4.4.2 Sediment samples
Samples were taken on different locations along the Guadalete river. Because all
locations were different not all measurements could be carried out on each
location. Table 3 Overview of the measurements shows exactly what measurements
were carried in each location.
0.00
0.20
0.40
0.60
0.80
1.00
-20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00
km downstream
Morphological Quality Index
26. 15
Measuring
point
Day visited Time
visited
Coordinates Cross-
section
Sediment
sample
SS
sample
-10 17.09.2013 13.20 N 36.48.504 W
005.19.729
YES Transect
line
NO
0 20.09.2013 11.30 Not available NO Bulk sample YES
20 17.09.2013 17.00 N 36.55.271 W
005.33.259
YES Bulk sample YES
30 18.09.2013 10.15 N 36.52.192 W
005.39.025
YES Bulk sample YES
40 19.09.2013 14.20 N 36.47.400 W
005.45.758
HALF NO YES
60 18.09.2013 13.20 N 36.44.657 W
005.48.087
YES Areal
sampling
YES
80 18.09.2013 15.00 N 36.41.608 W
005.51.487
YES Bulk sample YES
90 18.09.2013 16.20 N 36.38.851 W
005.55.823
NO NO YES
100 19.09.2013 12.00 N 36.37.786 W
005.59.208
NO Bulk sample YES
110 19.09.2013 9.45 N 36.37.730 W
006.08.182
NO Bulk sample YES
120 19.09.2013 11.15 N 36.35.947 W
006.13.258
NO Bulk sample NO
Table 3: Overview of the measurement points
Results
After all, the sample were collected they were analyzed in the lab to calculate the
grain size composition, D10, 50, 84 and 90 and a general description of the
samples. The results of this can be found in Appendix II: Grain size distribution.
With these results we can set up a graph, which depicts the D50 and D84 in µm
against measurement points (Graph 2).
27. 16
Graph 2: Grain size distribution
Underneath, a Hjulstrom diagram is displayed (Figure 8). It shows the relation
between flow velocity and sediments deposition, transport or erosion. This
diagram can be used to relate the flow velocities and grain sizes, taken form the
center of the river, to each other and determine which geomorphological process is
occurring at the given location. The exact values for velocities can be found in the
chapter of hydrology.
Figure 8: Hjulstrom graph (http://dlgb.files.wordpress.com/2008/09/hjulstrom_curve_task.jpg )
0.000
20.000
40.000
60.000
80.000
100.000
120.000
140.000
160.000
-50.00 0.00 50.00 100.00 150.00
Grainsize(micrometer)
Km downstream
Grain size
d50 (mm)
d84 (mm)
28. 17
From point 60 and upstream, the flow velocities are relatively high (93-122 cm/s).
As the Hjulstrom diagram shows, at these speeds only coarse materials remain
deposited. This corresponds with the data shown in the diagram below, were grain
sizes that have a d50 of 50 mm and higher. Downstream of point 80, the velocities
drop, and so do the grain sizes. The velocities related to the grain size (0.07-0.08
mm d50) show that transportation of these sediment sizes can occur, but no
erosion takes place. Point 80 is the odd one out; the velocity of 90 cm/s related to a
d50 of only 0.08 mm indicates erosion is taking place here. This might be the
explanation for the turbidity that was observed downstream from point 80, which
should not occur at this time of the year (due to no rainfall and lowering river
discharge). At point 80 two artificial structures were discharging a great amount of
water through a pipe connected to the Guadalcacin reservoir (Perscomm, J.
Benavente, 2013). This raised discharge Q at this point significantly, causing the
described conditions.
Graph 3: Velocity and grain size comparaison
Discussion
Because every measuring point was different, multiple gathering methods have
been applied for the gathering of the samples. This might lead to the discussion
about the accuracy of the results. However, it has been proven that the methods
that were used to gather the samples will yield the same results (L.B. Leopold
(1970)).
Also, for some locations it was impossible to gather a soil samples due to the lack
of required materials or the situation at the location. For example, it was
impossible to gather a soil sample from point 40 since the sediment consisted only
of boulders, which were impossible to gather with the available equipment. Point
90 failed as well due to a concrete paving and big water velocities below the
bridge.
0.000
10.000
20.000
30.000
40.000
50.000
60.000
70.000
80.000
90.000
100.000
0
20
40
60
80
100
120
140
-20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00
mm
cm/s
km downstream
Velocity & Grain size
V (cm/s)
d50 (mm)
d84 (mm)
29. 18
4.4.3 Cross-sections
In this paragraph cross sections in point -10, 20, 30, 60 and 80 are shown. Each
cross section consist of dry section measured by Geomorphology group and wet
section by Hydrology group. Coordinates are given in local system for each section.
In order to extrapolate a clear cross section point in XYZ coordinates has been
rotated and translated to a plane system (XZ) using both Math lab and Excel.
Results
In this following graphs you can find all the cross sections that were measured
during this field week. The coordinates on land were taken by different methods
by the geomorphology group and the hydrology group took the coordinates in the
water.
Graph 4: Point 10 – Cross Section
Graph 5: Point 20 – Cross Section
316.2
316.4
316.6
316.8
317
317.2
317.4
317.6
-70 -60 -50 -40 -30 -20 -10 0
z[m]
x [m]
Cross Section - Point -10
(local system)
97
98
99
100
101
102
103
104
105
106
-70 -60 -50 -40 -30 -20 -10 0
z[m]
x [m]
Cross Section - Point 20
(local system)
31. 20
Graph 8: Point 80 – Cross Section
Discussion
It can be seen that cross section are less than point measurement because of
technology problem: lack of GPS satellite covering or heavy presence of trees for a
clear total station collimation. In some cases DGPS survey has been done with a
higher than 0.5 m precision.
Local system can be changed in a global one only knowing at least the GPS
coordinates of two points: in many cases these was not possible to measure.
However, thanks to the elevation of the river bank assessed during post-analysis, it
is possible to estimate the elevation of the cross section.
4.4.5 Bank full discharge
As bankfull discharge is defined as the discharge that shaped the river bed,
geomorphological features are strictly related to this particular discharge. Bankfull
discharge is also statistically assessed as the discharge with return period of
between 1.58 and 2.33 years.
It is possible to assess the level of the bankfull discharge (ybd) observing
geomorphological features and vegetation. For examples the change in the lateral
slope of a cross section and the border between older vegetation and plants or
bushes younger than 2-3 years are natural indicators of that level. That level
defines the related wet area of the section (Abd).
In order to assess the discharge the steady flow velocity (V) can be calculated. The
approximation of steady flow velocity simplifies the method. The Manning’s
coefficient can be assessed with Limerinos (1970) that relates roughness with D84.
That formula is the best assessment for natural channels like Guadalete river. The
Bankfull discharge (Qbd) can be calculated as Qbd=V*Abd (G.H. Dury (1961)).
96.5
97
97.5
98
98.5
99
99.5
100
0 10 20 30 40 50 60
z[m]
x[m]
Cross Section - Point 80
(local system)
32. 21
Graph 9: Banfull Discharge of the Guadalete river
4.4.6 Slope
The general slope, local slope and elevation are shown in the following graphs.
Graph 10: Global Slope of the Guadalete river
-5
0
5
10
15
20
25
30
-20 0 20 40 60 80 100
BankfullQ(m3/s)
km downstream
Bankfull discharge
0
0.001
0.002
0.003
0.004
0.005
0.006
-20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00
km downstream
Global slope
33. 22
Graph 11: Elevation of the Guadalete river
Graph 12: Local slope of the Guadalete river basin
4.4.7 General discussion
During the surveys many observation related to the morphology of the area, in
terms of vegetation and morphological features, were taken. These will be very
important in order to assess the Hydro morphological quality of the river and for
post-analysis deductions
Sediment transport and the natural fluvial cycle of the Guadalete river has been
disturbed by artificial, human created structures, such as dams, weirs and water
catchment basins. The water discharge itself is not heavily constricted, but weirs
and dams cause sedimentation in water basins upstream of them. It was observed
in the field, that the river-bed downstream of these structures is covered with
rocks and had a lack of fine sediment. In addition, levees were observed in several
0
50
100
150
200
250
300
350
400
450
-20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00
mabovesealevel
km downstream
Elevation
0.0000
0.0010
0.0020
0.0030
0.0040
0.0050
0.0060
-20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00
km downstream
Local slope
34. 23
measurements points (mostly downstream), restricting the cross section area of
bank full discharge. The natural river bed geomorphological structure does not
seem to be heavily changed by human influence (besides the reservoirs), only the
delta area is canalized and has artificial banks surrounded by industrial areas.
One liter samples of suspended solids were taken, but not analyzed due to
Guadalete’s morphological qualities. The substrate situated next to river banks is
soft and bare; there is no low vegetation that could cover and hold in place soil
particles with its roots. Guadalete’s catchment area is prone to rainwater and wind
induced erosion, but the region of Andalusia sees significant amount of rainfall
only during the winter season. Therefore, the water column should not contain any
suspended soil particles, as the samples were taken at the end of summer (during
the dry season) and wind erosion is negligible.
It can be concluded that suspended solids found in water column are of biological
nature, a pollution of human and agricultural waste. Many settlements either do
not have any wastewater treatment plants or their plants are too old to meet
European water quality standards. Due to this, large amount of untreated sewage
is discharged in the Guadalete river. Also various pesticides and fertilizers are
discharged into the river from agricultural lands. One of the most common cultures
in the lowlands of the river basin is cotton, which requires large amounts of
irrigation.
35. 24
4.5 Conclusion
The sample locations were selected trough discussion with all the groups and they
were pointed out on a map. The smallest measured cross section had a size of
approx. 57 meters; the biggest measured cross section had a size of approx. 125
meters.
The compositions of the sediments across the cross sections were different
depending on the length the river already travelled. In the Zahara area there was
coarse gravel sediments, further downstream the sediment would change into
sand, mud and silt.
On some measuring points it was impossible to take sediment samples due to
human impact, structures would increase the velocity of the water. Some locations
were located after basins, which resulted in sediment samples only consisting of
boulders. Upstream the global slope of the river is 0.0056, in the middle stretch of
the river the global slope is 0.0019 and the global slope at the downstream part of
the river is 0.0006. This shows the global slope flattens towards the end of the
river.
After filling in the IDRIAM forms each measurement point gained a value for the
morphological quality index (MQI). The higher the MQI value, the better the
natural state of the river basin is. Lower MQI values mean that human impact is
high (like engineering constructions such as dikes, weirs, substrate, agriculture,
industry etc.). 50% of the MQI values were excellent. The only bad conditions were
created by human impact, and not through geological processes; so in general we
can conclude that the geomorphological condition of the river basin is good.
36. 25
5. Hydrology
The aim of the hydrological assessment and analysis is to determine the character
of the river flow and identify possible problems in the river basin. It is important to
determine to what degree the flow is regulated by existing artificial structures, if or
how the interaction with tidal forces is important, and the general properties and
dynamics of the river throughout its course in terms of flow rate, velocities and
dimensions. The acquired data can be used to develop a hydrologic model (using
SOBEK) to simulate the hydrologic dynamics of the river and provide better
insight. Such model will also provide the opportunity to estimate the effects of
changes in the current water system. Additionally, an estimation of the amount of
water diverted for irrigation is relevant. The geo-morphological and biological
analyses are also conducted. This happens in collaboration with other research
groups. Responsibilities are divided according to competencies, respectfully. All
obtained data can be compared to findings of previous studies, implementing data
on precipitation and groundwater.
Figure 9: Layout of the sampling points aong the Guadalete river
37. 26
5.1 Materials and methods
The target stretch of the river was divided in two parts - upstream and
downstream of point 60, which is located immediately downstream of the Boros
reservoir outlet.
The downstream section was surveyed with the OTT Qliner ultrasonic current
profiler. The sensor of the device is attached to a watertight miniature boat and is
equipped with a Bluetooth transmitter. The data is transmitted to a handheld
computer that plots the cross section and calculates the volumetric flow rate in
real time.
On site a cable has been stretched across the river, acting as a line of the cross
section. (figure 2) The Qliner has been then attached to the cable and transported
from one bank of the river to the other by means of a rope. The rope is then
stretched from both sides to stabilise the boat and released from one side to move
the boat to the next measurement vertical.
Figure 10: OTT QLiner method.
After installing the structure on site, velocity and depth are measured with the
Qliner for each section, depending on the width of the river (usually with 1 meter
distance, more for wider parts). The device starts at the point of 1.25 meters away
from the river bank and then measures the depth of the water and respective
velocity, saving the results into a handheld computer.
38. 27
Figure 11: Illutration of the Qliner method measurement
After the first measurement, the device is then moved (see Figure 11) with a step of
1 to 4 metres (depending on location) with the thinner rope and the next
measurement is then performed in the same way. This is repeated as many times
as it is needed to measure the cross-section.
The upstream section of the river was surveyed using less advanced techniques.
The depth of this part of the river was too low to measure using the Qliner. The
width of the cross-section was determined by stretching a measuring tape above
the water surface. Then a levelling pole was used to determine the water depth at
each step of the cross-section.
Afterwards, the electromagnetic velocity meter, the “flipper” was used to measure
the velocity in 3 different locations of the total width – in the middle and closer to
the margins of the stream width. The values are documented on paper and the
surveying continues at the next location.
Alternative method of measuring velocity without the electromagnetic flipper:
Using the measuring tape, a 10 meter distance is designated along the flow of the
river. Then a floating object is placed onto the surface of the water and the travel
time along that distance is measured to calculate velocity. A minimum of 4 said
tests is conducted in order to obtain more accurate data. This method only
measures the velocity of the surface of the stream, which can be converted to cross
section velocity.
In order to determine the flow rate Q (m3/s), two different parameters are
measured on the field, velocity (v) (either indicated by the electromagnetic flipper
or the alternative method) in m/s and the surface area (A) in m2 of each cross
section of the river. The following calculation is applied:
Q = v * A
39. 28
5.2 Results and discussion
The final product of field work is the calculated volumetric flow rate in the cross
section of each sample point along the river (see example in Figure 4). The values
are calculated from measured values for velocity and wetted area. Below, the
values for velocity and flow rate are presented in table 1.
Figure 12: Example cross-section including wet and dry section. Of point 20
40. 29
Measuring
point
Location Coordinates
Flow rate
m^3/s
Velocity
m/s
(centre of
the
stream)
0
Outflow of
Zahara
Reservoir
- 5,3 1,22
10
Between
Zahara and
Puerto
Serrano
- 5,7 0,73
20
Puerto
Serrano
N 36.55.271
W
005.33.259
5,7 1,10
30
Inflow of
Bornos
Reservoir
N 36.52.192
W
005.39.025
6 0,93
40
Outflow of
Bornos
Reservoir
N 36.47.400
W
005.45.758
7 1,19
60
Outflow of
Arcos
Reservoir
N 36.44.657
W
005.48.087
5,9 1,08
80
Juction with
Majacete
N 36.41.608
W
005.51.487
7,3 0,90
90
La Barca de
la Florida
N 36.38.851
W
005.55.823
9,5 0,41
95 PDA error (data lost)
100 El Torno
N 36.37.786
W
005.59.208
11,3 0,45
105
Landfill in
river
- 10,5 0,17
110
Downstream
tidal weir
N 36.37.730
W
006.08.182
(13,3) 0,13
120
El Puerto de
Santa Maria
N 36.35.947
W
006.13.258
(290)
Table 4: Measured velocities and calculated flow rates
41. 30
The flow rate values for River Guadalete show a gradual increase in flow towards
the mouth of the river. In comparison to the findings of a group of students from
the HZ University of Applied Sciences in September 2012, the flow rate has
drastically increased. The most probable cause is the excessive amount of
precipitation received during winter 2012/2013 in the area of the source of River
Guadalete. Graph 13 displays the calculated flow rates of the River along it’s course
(distance starting from first measuring point!).
Graph 13: measured velocities and calculated flow rates
SOBEK results
A hydrologic model has been constructed using the SOBEK software package. The
boundaries of the model are from point 0 to 120 inclusive. The stretch of the river
that is modelled is 95 km long and has a global slope of 50 meters across that
distance.
42. 31
Figure 13: Side view of the SOBEK model
Figure 13 depicts the side view of the model - at the upstream boundary of the
model at Arcos de la Frontera (point 0) the flow rate is set to 6 m3/s, which is
consistent with the measurements taken in the field. Twenty kilometres upstream
of the other boundary there is a weir that gates the influence of the tide. At the
downstream boundary (point 120) a tidal cycle was simulated using data acquired
from the internet. The dataset contains values of the water depth for every 10
minutes for the simulated period, which is from 17-09-2013 midnight till 21-09-
2013 midnight.
Figure 14 depicts the simulation results of the tidal influence. The model shows
that the hydrological impact of high tide would reach only about 5 kilometres
upstream if the weir was not present. That leads us to the conclusion that the
purpose of the weir is to improve water quality rather than regulating quantity,
namely prevention of salt-water intrusion into the stream.
Figure 14: Influence of the tidal weir
43. 32
In Figure 15: Velocity at point 110 you see that the velocity fluctuates between 0,15
m/s and 0,41 m/s due to the tidal influence. This point is situated directly
downstream of the tidal weir.
Figure 15: Velocity at point 110
In Figure 15: Velocity at point 120 you see that the velocity fluctuates between 0,48
m/s and -0,51 m/s due to the tidal influence. This point is situated downstream of
the tidal weir at the blue bridge in Puerto Santa Maria. Every tidal cycle there
enters seawater with a velocity 0,48 m/s the river basin of the Guadalete. Every
tidal cycle there is an outflow of water with a velocity of 0,51 m/s.
0_s41, Velocity (m/s)
TeeChart
21-09-201320-09-201319-09-201318-09-201317-09-2013
-0,14
-0,16
-0,18
-0,2
-0,22
-0,24
-0,26
-0,28
-0,3
-0,32
-0,34
-0,36
-0,38
-0,4
-0,42
44. 33
Figure 16: Velocity at point 120
As a result we have built a basic model of the current situation, which can be used
to calculate different scenario’s like the input of higher discharges from the
Guadalete River and the influence of taking out the tidal weir. Some kind of
calibration is done by comparing the measured data at the cross sections with the
data of the model at the cross sections.
0_s2, Velocity (m/s)
TeeChart
21-09-201320-09-201320-09-201320-09-201320-09-201319-09-201319-09-201319-09-201319-09-201318-09-201318-09-201318-09-201318-09-201317-09-201317-09-201317-09-201317-09-2013
0,5
0,4
0,3
0,2
0,1
0
-0,1
-0,2
-0,3
-0,4
-0,5
45. 34
5.2.1 Groundwater
The stream of the Guadalete River is made up of overflow of groundwater in the
mountains, which is mainly recharged by precipitation during wintertime. See
figure 5 below for the yearly distribution of precipitation.
Figure 17: Precipitation map Rio Guadalete River Basin (Source: Presentation Javier Gracia).
The river courses through 7 major aquifers in the investigated area. Because of the
geographical positioning rain occurs mainly in the mountain. There are seven
major aquifers feeding the Guadalete River and its tributaries. Groundwater
quality is strongly related to the type of substrate, human activity and saltwater
intrusion in the coastal areas. Variety in the groundwater quality brings about a
classification of the aquifers.
The table below shows a classification of the aquifers in terms of two most relevant
characteristics for human consumption: salinity and alkalinity. Groundwater
salinity in the Guadalete River Basin varies from low salinity water, suitable for
any tipe of crop (C1- <750 µS/cm) to extremely high salinity, suitable only for very
permeable soils and crops with high tolerance (C4 - >3000 µS/cm). In terms of
alkalinity groundwater has been cathegorized as low alkalinity (S1- <10 µS/cm,
suitable for any soil type and crop type, to extremely high (S4 - >29), generally
inadequetfor irrigation except when salinity is low and the soils are rich in
carbonates ( J.A. Lopez Geta…et al, 2005).
46. 35
Aquifer Type
Input*
(
)
Output**
(
)
Salinity Alkalinity
El Puerto
Del Santa
Maria
Detrital*** 7.6 4 C4 S1
Jerez de la
Frontera
Detrital 15 2 C4 -
Aluvial del
Guadalete
Detrital 24 9 C3 -
Arcos-
Bornos-
Espera
Detrital 7.6 4 C1 S1
Llanos de
Villamartin
Detrital 11.6 7.3 C1-C3 S1
Aquifer de la
Sierra de
Grazalema
Carbonate 63.1 2.4 C1 S1
Sierras de
las Cabras
Carbonate 9.5 1.45 C1 S1
Table 5: Main aquifers in the Guadalete River Basin (Source: Lopez Geta, 2005)
*input= rain infiltration and ground water (lateral) input
**output= exploitation by pumping and springs
***detrital=in direct communication with the river
Figure 18: Main aquifers in the Guadalete River Basin (Source: Presentation Javier Gracia).
47. 36
Those aquifers and the Guadalete River are in constant interaction, although the
exchange of water varies over the seasons. The detrital aquifers connect directly to
the river, meaning that the water is seeping in and out through pores in the
substrate. Carbonate aquifers interact with the River through other (small)
streams. Next to water from surface water, also groundwater is being pumped to
be used as either drinking or irrigation water, whereas most irrigation water is
derived from surface water. Drinking water is partly supplied by groundwater in
the east (upstream) part of the River Basin and by surface water in the coastal,
western part (downstream). Groundwater quality is strongly related to the type of
substrate, human activity and salt water intrusion in the coastal areas. (Lopez Geta,
2005).
The obtained data on volumetric flow rate in the Guadalete River does not suggest
any major recharge of the aquifers by the river downstream of the reservoirs. The
flow rate increases gradually with the distance from the source. Reasons for that
are tributaries entering the river and also a shift towards more porous soil in the
western part of the river basin, allowing more groundwater flow (lecture Javier
Garcia). Dam management always has an impact on the flow rate in the river.
5.2.2 Measurement accuracy issues
Due to the high depth range in some cross sections the Qliner has had difficulties
plotting the correct cross section and thus determining the flow rate accurately
was difficult. Some verticals had to be verified using traditional methods such as a
rope with a heavy object and measuring tape. Other verticals were simply
interpolated with the adjacent ones (only in shallow parts). Given that the
methodology of surveying requires personnel to be present on both sides of the
stream most cross sections were measured immediately downstream of a bridge.
Turbulence caused by the pillars of a bridge could have slightly interfered with the
measurement results. Additionally for the same reason of complexity of the
measurement setup some cross sections had to be relocated from the originally
agreed coordinates or cancelled altogether.
Another aspect that had an effect on measurement accuracy was the arching of the
cable holding the Qliner. Also the method of measuring the distance in between the
cross section verticals had an accuracy range of up to 10% depending on the
velocity of the current.
It was impossible to measure the correct flow rate at the estuary (point 120) due
to the constant strong tidal influence. Also at low tide the water was too shallow to
measure with the Qliner. However, the cross section was plotted during high tide.
The suspiciously high flow rate value at that point can be explained by the tidal
inflow of seawater at the time of measurement.
The flipper was mainly used for upstream, but although it is also a very accurate
device, its extreme sensitivity resulted in error results in most of the locations. In
the end, only one point could be accurately measured using the device and the
following ones were measured with the least accurate method, the alternative one.
48. 37
The method introduced various weak points in measurement at once – the time
and the distance measurements as well as depth measurement have approximately
10% error margin each.
5.2.3 Other discussion points
Regarding the timeline of the measurements, it was conducted during 3 days (17,
18 and 19 of September), from the time period between 9 to 17 hours and the
main river points were mostly measured at the first 2 days (17 and 18). The last
day was left to concentrate on some of the most problematic points and measure
some side sources of inflow.
Initially it was decided that the hydrology assessment of the river would be made
in 13 points of the river (from point 0 which is the inlet of the Zahara reservoir to
point 120 which is the outlet of the river), however, some points were standing in
private properties which the students had no authorization to enter, and so they
were discarded.
5.2.4 Tidal influence
The last point of the tidal influence is situated in El Portal, 16 km from the river
mouth. Downstream from El Portal there is a weir that does not allow tidal water
to advance.
During those days measurements were carried out, the tidal range at Cadiz was
about 3 metres. The inflowing and outflowing seawater highly affects the
measured velocity and depth of the river, and therefore the flow rate. At all points
influenced by the tide it is therefore difficult to determine the actual flow rate of
the river. A measurement carried out during high tide (inflowing) at Point 120
yielded a flow rate of 290 m³/s, which indicates the vast influence the tide has on
the water system of the river (until the weir at El Portal) (see table for results).
5.2.5 Weather
According to the weather reports (weather.com) there has been 31 mm of rain
starting from July, but there is still no water shortage, as the precipitation amount
was enough previously during the winter and spring. Also the flow rate is greater
than the flow rate according to the research of the year 2012 probably for the same
reason.
49. 38
5.3 Conclusion
Measurement results have led to the conclusion that the hydrology of the
Guadalete River is entirely controlled through engineering at the time of the
assessment, although the situation could be different during the high-rain season.
River Guadalete is a rather small river not suitable for any kind of shipping. The
tidal area is influencing the river Guadalete up until the weir outside of El Portal
which is approx. 20 km upstream of the estuary. This part is also artificial because
the ditch is kept at a depth of 5 meter so the ships can enter Puerto Santa Maria.
After El Portal it looks like the river is still meandering. The flow rate in the river is
not controlled by natural processes but is by the flow rate of the water reservoirs
Archos, Bornos and Zahara and the height of the weir at El Portal. This state is
human engineered therefore it is anthropologic.
50. 39
6. Chemistry
6.1. Methods and Material
The examined area is in between the inlet of the Guadalete into the Zahara
reservoir and the mouth of the river at El Puerto de Santa Maria. 26 samples were
taken in the river. The stratification of the Bornos reservoir was also examined. For
the chemical analysis of the Guadalete River basin two types of analysis were used:
field analysis and laboratory analysis. The samples were taken at the following
points:
Figure 19: Map of the sampling points from the inlet of Zahara till Puerto de Santa Maria.
51. 40
point
name
distan
ce
from
point
0 [km]
Meas
ured
yes/n
o
Location Reason
-10 -10,232
Yes Base point before Zahara
reservoir
Basepoint
0 0 Yes After Zahara reservoir Basepoint
15 26,522 Yes Before Puerto Serrano No WWTP at Puerto Serrano
20 28,647 Yes After Puerto Serrano No WWTP at Puerto Serrano
30 42,28 Yes Before Bornos reservoir Inflow reservoir
35 53,775
Yes At Bornos in the reservoir (also
measured stratification here)
No WWTP at Bornos
40 56,695 Yes After Bornos reservoir Outflow reservoir
60 64,075 Yes After Archos reservoir Outflow reservoir
70 80,167
No River from Espera coming
together with Guadalete
No WWTP at Espera
80 81,739
Yes Majaceite River joining
Guadalete River
2 big rivers joining together
90 93,914
No La barca de la Florida Was same water as at point
95
95
101,37
2
Yes Before Tornos No WWTP at Tornos
100
107,23
9
Yes After Tornos No WWTP at Tornos
105
110,98
9
Yes Arroyo de las Cruces joining
Guadalete river
Large river joining
107
125,01
5
Yes Before WWTP Before WWTP
109 yes Effluent WWTP Effluent WWTP
110
129,80
5
Yes After WWTP After WWTP
111
131,88
4
yes Intertidal area Intertidal area
112 134,46 yes Intertidal area Intertidal area
113
136,07
8
yes Intertidal area Intertidal area
114
137,30
2
yes Intertidal area Intertidal area
115
137,90
9
yes Intertidal area Intertidal area
116
140,67
4
yes Intertidal area Intertidal area
120
145,00
6
yes Foot bridge el Puerto de Santa
Maria
Intertidal area
130
147,85
7
yes Mouth of the river Intertidal area
Table 6: table of the sampling points from the inlet of Zahara till Puerto de Santa Maria.
52. 41
The samples taken in the field were done by dropping a sampling bucket from a
bridge or by throwing the bucket from the riverbank and pulling it back with a
rope. The field measurements were taken from within the bucket and a sample
bottle was filled each time, so that it could be taken to the laboratory for further
analysis. In the estuary, a boat was used and the field measurements (points 111 to
120) were taken directly from the estuary. The sample bottle was filled with no air
inside to prevent any other chemical reactions during transit.
When the reservoir sampling was done, the field measurements were done in the
water in the water sampler, to prevent oxygen entering the water during
measurements.
The analysis taken in the field were:
Conductivity (in μS/cm)
Temperature (in oC)
pH
Oxygen concentration (in mg/L)
Oxygen Saturation (in %)
Hach-Lange spectrophotometer was used for the chemical analysis in the
laboratory. The parameters analyzed with the Hach-Lange spectrophotometer
were:
Ammonium (NH4+-N)
Nitrite (NO2--N)
Nitrate (NO3--N)
Total Nitrogen (N-total)
Phosphate (PO43-)
Total Phosphorus (P-total)
The materials we used in the field and lab are listed in the appendix
The methods for analyzing the various chemical contents in the sample water are
attached in the appendix.
53. 42
6.2 Results & Discussion
6.2.1 Oxygen
Oxygen concentration in Guadalete River was fairly good in all 26 sampling points.
It was clearly above the EU standard for surface water, which is minimum 5 mg/L,
see Graph 14.
Compared to measurements made in 2012 downstream Arcos dam (point 60), the
situation has improved. In 2012, there was not enough oxygen downstream the
dam (Bachelor students of Water Management in HZ, 2012). There have been more
rain in the winter of 2012-13 than in previous winters, and the water level in the
river is higher in 2013. This might contribute to the better oxygen situation, since
water from Arcos reservoir might be released over the dam this year.
Graph 14: Oxygen Concentration
54. 43
6.2.2 pH
As seen in the Graph 15, the pH over the river’s course is fairly stable with
difference of 0.97 between the lowest value at the point 110 and the highest value
(8.67) at the point 60. In addition, in 2012, pH values were lower than this year
(the minimum in 2012 was around 7, and in 2013 it was more than 7.6), as were
the oxygen concentrations. As expected, pH values were following closely the O2
values: pH is lowered by high CO2 concentrations in the water, and when there is
plenty of oxygen in the water, it can mean that it is not consumed by CO2 producing
organisms.
Graph 15: pH of the Guadalete river
55. 44
6.2.3 Conductivity
Graph 16: Conductivity of the Guadalete river
As seen in graph 16 the conductivity along the river’s course slowly increases,
starting from 1043 μS/cm at point -10 at Zahara inlet and reaches 1326 μS/cm at
point 80A. At this point, Guadalete River mixes with Majaceite River (point 80B),
which has a conductivity of 729 μS/cm. Downstream of the river junction, the
water dilutes to 1139 μS/cm at point 80C. The conductivity then slowly increases
again, until it reaches its highest point right after the water treatment plant at
point 110. After this the water flows over the tidal weir and into the estuary. At the
estuary during the time of sampling, the current was still flowing downstream. At
point 115 the current changed as the tide started to push back up the estuary
where the conductivity increased to above 20 000 μS/cm. 2
At point 116/116B two measurements were taken, because the tide seemed to be
rising on the Western side of the river more: the water was greenish, compared to
gray water on the Eastern side. On the Western side the conductivity was 20 400
μS/cm and on the Eastern side 18 41 μS/cm. Also in Puerto de Santa Maria two
measurements were made, with two hours’ interval. At the first measurement,
conductivity was 20 100 μS/cm, while at the second time it was 34 100 μS/cm. The
differences where expected, since salinity is closely related to conductivity.
2 On the sampling day, low tide was at 08:55 and the high tide at 15:09, and the measurements were made
between 10 and 12:30.
56. 45
6.2.4 Nitrogen
Graph 17: Nitrogen levels in the Guadalete river
The main finding was that nitrogen levels after the water treatment plant in Jerez
peaked, and the total nitrogen concentration exceeded the EU standard, 8.29 mg/L,
when standard is maximum 2.2 mg/L. High total nitrogen concentrations were
found everywhere downstream from the water treatment plant (point 110) until
the river water started to change to saline due to rising tide at the time of
sampling, see Graph 17
There was a sudden drop, from 8.29 mg/L to 3.16 mg/L in the concentration of
total nitrogen after the tidal weir (point 111). It seems that the tide reaches all the
way to the weir and dilutes the nitrogen concentrations.
Especially ammonium concentrations peaked after the water treatment plant. In
addition, the effluent water of the waste water treatment plant, with a total
nitrogen level of 46.60 mg/L, exceeded the EU standard of effluent water for
WWTP of 10 mg/L.
No clear effect of agriculture or other industry than waste water treatment plant
on the nitrogen concentrations was observed in this study.
-10
0
15
20
30
3540
60
80A
80B
80C
95
100
105
107
115
116
120
120B
-10 0
1520 30
35 40
60 80A
95
100
105 107
110
112
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.0
0.5
1.0
1.5
2.0
2.5
-10 10 30 50 70 90 110 130 150
NO2
−(mgN/l)
NH4
+,NO3
-,Ntot(mgN/l)
Distance (km)
Ammonium
Nitrate
Total
nitrogen
Standard
Nitrite
WWTP effluent,
Ntot
= 46.6 mg/l
57. 46
6.2.5 Phosphorus
Total phosphorus values exceeded EU standard for surface water (<0.15 mg/L) in
several places: after Villamartín (point 30), at the Bornos reservoir (35), upstream
of Junta de los Rios (the junction of the rivers Guadalete and Majaceite, point 80A),
and just before the water treatment plant and especially after it (107, 110). (See
Graph 18)
Graph 17: Nitrogen concentration of the Guadalete river.
Just after the waste water treatment plant the total phosphorus concentration was
more than two times the EU standard, or 0.345 mg/L. In addition the effluent
water of the waste water treatment plant, with a total phosphorus concentration of
1.5 mg/L, exceeded the EU standard of effluent water for WWTP of 1.0 mg/L. The
concentration dropped after the tidal weir (111), and continued to decrease
downstream, where the river water was diluted by the rising sea water (at the time
of sampling).
Upstream of Junta de los Rios, a small stream of soapy water was observed at the
time of sampling, which might explain the phosphorus concentration. It is not clear
why increased phosphorus levels were not measured after Puerto Serrano (point
20) that does not have a water treatment plant, but at the next sampling point in
Villamartín (point 30) the concentration of total phosphorus was 0.486 mg/l,
which is more than three times the EU standard maximum. It is possible that the
elevated phosphorus concentrations where temporary, but without new
measurements it cannot be sure.
No clear effect of agriculture or other industry than wastewater treatment plant on
the phosphorus concentrations was observed in this study.
-10 0 15 20
30
35
40
60
80A
80B
80C
95
100
105
107
110
111
112
113
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
-10 40 90 140
Ptot(mg/l)
Distance (km)
WWTP
effluent,
1.5 mg/l
Graph 18: Phosphorus concentration of the Guadalete river
58. 47
6.2.6 Lake stratification in Bornos reservoir
Samples were taken from Bornos reservoir at a point where the reservoir was 15.5
meter deep. The samples were taken at every meter of the water column. Very
clear stratification was observed. As seen in Graph 19, thermocline (a layer of
sudden change in the water temperature) is somewhere between 14 and 13 meter
deep.
Graph 19: Stratification of the temperature in Bornos reservoir
Because of the stratification, the bottom of the reservoir was completely oxygen
deprived. O2 values were 0.05 mg/L or less at 12 meter’s depth and below. At 11
meter’s depth the oxygen level was already 4.37 mg/L and rose quickly to over 6
mg/L, after which the increase of O2 concentration was slower. (see Graph 20)
Graph 20: Stratification of the oxygen in Bornos reservoir
-16
-14
-12
-10
-8
-6
-4
-2
0
20 21 22 23 24 25
Depth(m)
T (°C)
-16
-14
-12
-10
-8
-6
-4
-2
0
0 2 4 6 8
Depth(m)
O2 (mg/L)
59. 48
The pH values showed the same, layered behavior. As seen in Graph 21, there was
a clear chemocline around 10 to 12 meter’s depth.
Graph 21: Stratification of the pH in Bornos reservoir
-16
-14
-12
-10
-8
-6
-4
-2
0
7.20 7.40 7.60 7.80 8.00
Depth(m)
pH
60. 49
6.3 Conclusion
The waste water treatment plant in Jerez is the main pollution source in Guadalete
River, at the time when the nutrients concentrations are measured. The effluent
water of the WWTP exceeded the EU standards for effluent water of WWTP in both
total Nitrogen and total Phosphate. The water quality was fairly good before the
treatment plant, except for some peaks in total phosphorus concentration, which
might be temporary. No clear effect of agriculture or other industry than the
wastewater treatment plant on the nutrient concentrations was observed.
Based on the measurements and comparisons with the earlier study, it seems that
oxygen levels are better when there is more water in the river.
Bornos reservoir was stratified. Based on that observation, it is possible to assume
that Arcos reservoir would also be stratified, since it is a similar reservoir
according to measurements taken. It might be that in dryer years, no water from
the epilimnion is released but some water from the hypolimnion, which is oxygen
deficient. This could contribute to low oxygen levels in 2012, but not in 2013, when
some water was released from the epilimnion of the reservoir.
6.4 Comparison
6.4.1 Conductivity
Conductivity was similar in most of the sampling points in 2012 and 2013. But in
the estuary of Puerto de Santa Maria the conductivity in 2013 is almost double and
this can be due to the tidal influence.
6.4.2 Ammonium
There were nine similar sampling points in 2012 and 2013. The names of the
similar points are Arcos Dam, Majaceite river, before Torno, after Torno, before
Jerez, after Jerez, Jerez waste water treatment plant, Puerto de Santa María and
WWTP effluent. The conditions that were different this year were:
1. 2013 experienced more rainfall than 2012.
2. Flow of the water in the river was much higher in 2013 than in 2012.
Ammonium concentration in the Arcos Dam was very high last year as compared
to this year result. The value can be seen in the appendix. The flow was lower and
suspended solids had more time to digest and release ammonia. Ammonium
concentration in the estuary in Puerto de Santa María was much higher in 2012
than in 2013. While taking samples in 2013, we had incoming tides that diluted the
water, whereas it is likely that in 2012 they sampled during the outgoing tide. The
ammonium concentration in other sampling points did not differ much.
61. 50
6.4.3 Nitrate
The concentration of nitrate in 2012 and 2013 was similar in the above mentioned
sampling points. After the Jerez WWTP the nitrate concentration is quite higher in
2013 and this could be just a fluctuation.
6.4.4 Nitrite
Nitrite concentration in all sampling points in 2013 was lower than in 2012. This
could be because of more flow and more aeration in the river.
6.4.5 Orthophosphate
Orthophosphate concentration in Arcos Dam was significantly higher in 2012
62. 51
7. Biology
7.1 Materials & Methods
The Aim of this chapter is to have a detailed study of the relation between human
activity and the biology in the river Guadalete located in south of Spain. Biological
assessment will be addressed by determining the occurrence of bio-indicators at
several locations in order to find causal relationships between the human factors
and the biological state of the river.
Biology is the study of living organisms. These living organisms live in relation of
their environment; all organisms demand certain aspects of their environment.
Also organisms may alter their environment to make it more suitable for
themselves or other organisms. Biological assessments can be used to directly
measure the overall biological integrity of an aquatic community and the
synergistic effects of stressors on the aquatic biota residing in a water-body where
there are well-developed biological assessment programs (Figure 20, USEPA
2003). Resident biota functions as continual monitors of environmental quality,
increasing the sensitivity of the assessments by providing a continuous measure of
exposure to stressors and access to responses from species that cannot be reared
in the laboratory. This increases the likelihood of detecting the effects of episodic
events (e.g. spills, dumping, treatment plant malfunctions), toxic nonpoint source
(NPS) pollution (e.g. agricultural pesticides), cumulative pollution (i.e. multiple
impacts over time or continuous low-level stress), nontoxic mechanisms of impact
(e.g. trophic structure changes due to nutrient enrichment), or other impacts that
periodic chemical sampling might not detect. Biotic response to Impacts on the
physical habitat such as sedimentation from storm water runoff and physical
habitat alterations from dredging, filling, and channelization can also be detected
using biological assessments.
Figure 20: Biological assessments provide information on the cumulative effects on aquatic communities from
multiple stressors. (USEPA, 2003).
