Presents the likely impact of climate change on groundwater resources and methodology to assess the impact of climate change on groundwater resources.

1. Impact of Climate ChangeImpact of Climate Change
on Groundwater Systemon Groundwater System
C. P. KumarC. P. Kumar
Scientist ‘G’Scientist ‘G’
National Institute of HydrologyNational Institute of Hydrology
Roorkee – 247667 (Uttarakhand)Roorkee – 247667 (Uttarakhand)
13-14 November, 201513-14 November, 2015

2. Why include groundwater in
climate change studies?
Although groundwater accounts for small
percentage of Earth’s total water,
groundwater comprises approximately thirty
percent of the Earth’s freshwater.
Groundwater is the primary source of water
for over 1.5 billion people worldwide.
Depletion of groundwater may be the most
substantial threat to irrigated agriculture,
exceeding even the buildup of salts in soils.
(Alley, et al., 2002)

3. What is Climate Change?
IPCC usage:
•Any change in climate over time, whether due to
natural variability or from human activity.
Alternate:
•Change of climate, attributed directly or
indirectly to human activity, that
•Alters composition of global atmosphere and
•Is in addition to natural climate variability observed
over comparable time periods

5. GLOBAL CIRCULATION MODELS
Formulated to simulate climate sensitivity to increased
concentrations of greenhouse gases such as carbon
dioxide, methane and nitrous oxide.

6. Fundamental equations
in climate models
Atmosphere general circulation
models (AGCMs)
Ocean general circulation models
(OGCMs)
Coupled atmosphere-ocean
general circulation models
(AOGCMs)
Types of climate models
Numerical discretization in AOGCMs

7. -0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1880 1900 1920 1940 1960 1980 2000
Year
∆MeanTemperature(°C)
Recorded Worldwide Temperatures

8. GLOBAL CLIMATE CHANGE OVER LAST CENTURY
- 1 .0
- 0 .5
0 .0
0 .5
1 .0
Temperatureanomaly(oC)
- 1 .0
- 0 .5
0 .0
0 .5
1 .0
1 8 5 0 1 8 7 5 1 9 0 0 1 9 2 5 1 9 5 0 1 9 7 5 2 0 0 0
Y e a r s

9. 9
PROJECTED SURFACE TEMPERATUREPROJECTED SURFACE TEMPERATURE
CHANGESCHANGES
(2090-2099 relative to 1980-1999)(2090-2099 relative to 1980-1999)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
(o
C)
Continued emissions would lead to further warming
of 1.1ºC to 6.4ºC over the 21st
century
(best estimates: 1.8ºC - 4ºC)

10. Some areas are projected to become wetter,
others drier with an overall increase projected.
Source: IPCC, 2007
White areas have disagreement among models.
Annual mean precipitation change: 2071 to 2100 Relative to 1990
Winters (Dec-Feb) Monsoon (Jun-Aug)

11. Sea-Level Rise
• Global sea-level change results mainly from two
processes, mostly related to recent climate
change, that alter the volume of water in the
global ocean through -
• a) thermal expansion and
• b) the exchange of water between oceans and
other reservoirs (glaciers and ice caps, ice
sheets, other land water reservoirs, including
through anthropogenic change in land hydrology
and the atmosphere).

12. Sea Level Rise

13. Other Observations of Change in
Global Climate
 Globally, hot days, hot nights, and heat waves have
become more frequent.
 Frequency of heavy precipitation events has
increased over most land areas.
In Future…
 Tropical cyclones to become more intense, with
heavier precipitation.
 Snow cover is projected to contract.
 Hot extremes, heat waves, and heavy precipitation
events will become more frequent.

14. Climate Change Impacts -
General
Climate Change Impacts - Water
Resources

16. Impact of Climate Change on Water Resources & Hydrologic
Cycle

17. Overview of the Climate Change Problem
Source: IPCC Synthesis Report 2001

18. Climate Change Scenarios for South Asia
CO2 levels: 393 ppm by 2020; 543 ppm by 2050 and 789 ppm by 2080
Source: IPCC, 2007
Period Temperature, C Precipitation, %
DJF
(rabi)
JJA
(kharif)
DJF
(rabi)
JJA
(kharif)
2010-2039 1.17 0.54 -3 5
2040-2069 3.16 1.71 0 13
2070-2099 5.44 3.14 -16 26

19. TRENDS OF CLIMATE CHANGE IN INDIA

20. Rainfall
No clear trend in average annual rainfall over the country
1 8 7 0 1 8 8 0 1 8 9 0 1 9 0 0 1 9 1 0 1 9 2 0 1 9 3 0 1 9 4 0 1 9 5 0 1 9 6 0 1 9 7 0 1 9 8 0 1 9 9 0 2 0 0 0
- 3 0
- 2 0
- 1 0
0
1 0
2 0
3 0
RainfallAnomaly(%ofmean)
- 3 0
- 2 0
- 1 0
0
1 0
2 0
3 0
Y e a r s
All India summer monsoon rainfall anomalies (1871-1999)

21. 68%
22
10Annual rainfall shows decreasingAnnual rainfall shows decreasing
tendency in recent times over ~68%tendency in recent times over ~68%
area of the country.area of the country.
Sontakke, H.N. Singh, N. Singh,Sontakke, H.N. Singh, N. Singh,
Indian Institute of TropicalIndian Institute of Tropical
Meteorology, Research Report No.Meteorology, Research Report No.
PR-121, May 2008PR-121, May 2008
Rainfall variations across India during 1813 – 2006

22. Heavy rainfall events
(>10cm)
Very heavy rainfall
events (>15cm)
Heavy precipitation events over Central
India have increased during last 50
years
Source: IITM, Goswami et al. 2006
Light to moderate rainfall
events (5-100 mm)

23. 23
• Glacier melt projected to increase flooding and rock
avalanches and to affect water resources within the next
2 to 3 decades.
• Salinity of groundwater especially along the coast, due to
increases in sea level and over-exploitation.
• In India, gross per capita water availability will decline from
1820 m3
/yr in 2001 to 1140 m3
/yr in 2050.
IMPACTS ON WATERIMPACTS ON WATER
RESOURCESRESOURCES

24. Sea Level Rise in India
• Observations based on tide gauge
measurements along the Indian coast, for a
period of 20 years and more, for which
significantly consistent data are available,
indicate that -
• the sea level along the Indian coast has
been rising at the rate of about 1.3 mm/year
on an average.

25. In coastal areas there is a naturalIn coastal areas there is a natural
balance between salt and freshwaterbalance between salt and freshwater
f r e s h g r o u n d w a t e r
g r o u n d s u r f a c e
s a l in e g r o u n d w a t e r
s e a
p h r e a t ic w a t e r t a b le
z o n e o f d iffu s io n
im p e r v io u s la y e r

26. Hydrological Impact of Climate Change
 Temperature increases affect the hydrologic cycle by directly increasing
evaporation of available surface water and vegetation transpiration.
 Consequently, these changes can influence precipitation amounts, timings and
intensity rates, and indirectly impact the flux and storage of water in surface and
subsurface reservoirs (i.e., lakes, soil moisture, groundwater).
 In addition, there may be other associated impacts, such as sea water intrusion,
water quality deterioration, potable water shortage, etc.
 While climate change affects surface water resources directly through changes in
the major long-term climate variables such as air temperature, precipitation, and
evapotranspiration, the relationship between the changing climate variables and
groundwater is more complicated and poorly understood.

27.  The greater variability in rainfall could mean more frequent and prolonged periods
of high or low groundwater levels, and saline intrusion in coastal aquifers due to sea
level rise and resource reduction.
 Groundwater resources are related to climate change through the direct
interaction with surface water resources, such as lakes and rivers, and indirectly
through the recharge process.
 The direct effect of climate change on groundwater resources depends upon the
change in the volume and distribution of groundwater recharge.
 Therefore, quantifying the impact of climate change on groundwater resources
requires not only reliable forecasting of changes in the major climatic variables, but
also accurate estimation of groundwater recharge.

28. CLIMATE CHANGE IMPACTS ON GROUNDWATERCLIMATE CHANGE IMPACTS ON GROUNDWATER
- Recharge
- Discharge
- Storage
- Quality
- Temperature
- Precipitation
- Evapotranspiration
- Sea level rise
- Soil moisture

29. Issues on Groundwater Use
In addition, CLIMATE CHANGE impact may add existing pressure on
groundwater by i) impeding recharge capacities; ii) being called on
to fill eventual gaps in surface water availability due to increased
variability in precipitation; iii) groundwater contamination.
Major problems related with groundwater use are:
<Issues due to over-exploitation of groundwater>
 Depletion in groundwater table
 Land subsidence
 Saline water intrusion
<Issues on groundwater contamination>
 Human health damage
 Abandonment of well leading to decrease of water availability

30. Climate change could affect groundwater sustainability in several ways, including
(1) changes in groundwater recharge resulting from seasonal and decadal changes
in precipitation and temperature,
(2) more severe and longer lasting droughts,
(3) changes in evapotranspiration due to changes in temperature and vegetation,
(4) possible increased demands for ground water as a backup source of water
supply or for further economical (agricultural) development,
(5) sea water intrusion in low-lying coastal areas due to rising sea levels and
reduced groundwater recharge that may lead a deterioration of the groundwater
quality there.
Because groundwater systems tend to respond much more slowly to long-term
variability in climate conditions than surface-water systems, their management
requires special long-term ahead-planning.
Impact of Climate Change on Groundwater

31. (a) Soil Moisture
 The amount of water stored in the soil is fundamentally important to agriculture
and has an influence on the rate of actual evaporation, groundwater recharge,
and generation of runoff.
 The local effects of climate change on soil moisture, however, will vary not only
with the degree of climate change but also with soil characteristics. The water-
holding capacity of soil will affect possible changes in soil moisture deficits; the
lower the capacity, the greater the sensitivity to climate change. For example,
sand has lower field capacity than clay.
 Climate change may also affect soil characteristics, perhaps through changes
in cracking, which in turn may affect soil moisture storage properties.

32. (b) Groundwater Recharge
 Groundwater is the major source of water across much of the world, particularly
in rural areas in arid and semi-arid regions, but there has been very little
research on the potential effects of climate change.
 Aquifers generally are replenished by effective rainfall, rivers, and lakes. This
water may reach the aquifer rapidly, through macro-pores or fissures, or more
slowly by infiltrating through soils and permeable rocks overlying the aquifer.
 A change in the amount of effective rainfall will alter recharge, but so will a
change in the duration of the recharge season. Increased winter rainfall, as
projected under most scenarios for mid-latitudes, generally is likely to result in
increased groundwater recharge.
 However, higher evaporation may mean that soil deficits persist for longer and
commence earlier, offsetting an increase in total effective rainfall.

33.  Various types of aquifers will be recharged differently. The main types are
unconfined and confined aquifers.
 An unconfined aquifer is recharged directly by local rainfall, rivers, and lakes,
and the rate of recharge will be influenced by the permeability of overlying rocks
and soils.
 Unconfined aquifers are sensitive to local climate change, abstraction, and
seawater intrusion. However, quantification of recharge is complicated by the
characteristics of the aquifers themselves as well as overlying rocks and soils.
 A confined aquifer, on the other hand, is characterized by an overlying bed
that is impermeable, and local rainfall does not influence the aquifer. It is
normally recharged from lakes, rivers, and rainfall that may occur at distances
ranging from a few kilometers to thousands of kilometers.

34.  Several approaches can be used to estimate recharge based on surface water,
unsaturated zone and groundwater data. Among these approaches, numerical
modelling is the only tool that can predict recharge.
 Modelling is also extremely useful for identifying the relative importance of different
controls on recharge, provided that the model realistically accounts for all the
processes involved.
 However, the accuracy of recharge estimates depends largely on the availability of
high quality hydrogeologic and climatic data.
 The medium through which recharge takes place often is poorly known and very
heterogeneous, again challenging recharge modelling.
 Determining the potential impact of climate change on groundwater resources, in
particular, is difficult due to the complexity of the recharge process, and the variation
of recharge within and between different climatic zones.
 In general, there is a need to intensify research on modeling techniques, aquifer
characteristics, recharge rates, and seawater intrusion, as well as monitoring of
groundwater abstractions.

35. (c) Coastal Aquifers
 Coastal aquifers are important sources of freshwater. However, salinity
intrusion can be a major problem in these zones. Changes in climatic variables
can significantly alter groundwater recharge rates for major aquifer systems and
thus affect the availability of fresh groundwater.
 Sea-level rise will cause saline intrusion into coastal aquifers, with the amount
of intrusion depending on local groundwater gradients.
 For many small island states, seawater intrusion into freshwater aquifers has
been observed as a result of overpumping of aquifers. Any sea-level rise would
worsen the situation.

36.  A link between rising sea level and changes in the water balance is suggested
by a general description of the hydraulics of groundwater discharge at the coast.
 The shape of the water table and the depth to the freshwater/saline interface
are controlled by the difference in density between freshwater and salt water, the
rate of freshwater discharge and the hydraulic properties of the aquifer.
 To assess the impacts of potential climate change on fresh groundwater
resources, we should focus on changes in groundwater recharge and impact of
sea level rise on the loss of fresh groundwater resources in water resources
stressed coastal aquifers.

37. Methodology to Assess the Impact of Climate Change
on Groundwater System
The methodology consists of three main steps.
 To begin with, climate scenarios can be formulated for the future years
such as 2050 and 2100.
 Secondly, based on these scenarios and present situation, seasonal and
annual recharges are simulated with the UnSat Suite (HELP module for
recharge) or WetSpass model.
 Finally, the annual recharge outputs from UnSat Suite or WetSpass model
are used to simulate groundwater system conditions using steady-state
groundwater model setups, such as MODFLOW, for the present condition
and for the future years.

38. Objective
The influence of climate changes on goundwater levels and salinity, due
to:
a. Sea level rise
b. Changes in precipitation and temperature
Methodology
1. Develop and calibrate a density-dependent numerical groundwater flow
model that matches hydraulic head and concentration distributions in
the aquifer.
2. Estimate changes in sea level, temperature and precipitation
downscaled from GCM outputs.
3. Estimate changes in groundwater recharge.
4. Apply sea level rise and changes in recharge to numerical groundwater
model and make predictions for changes in groundwater levels and
salinity distribution.

39. The main tasks that are involved in such a study are:
 Describe hydrogeology of the study area.
 Analyze climate data from weather stations and modelled GCM, and
build future predicted climate change datasets with temperature,
precipitation and solar radiation variables (downscaled to the study
area).
 Define methodology for estimating changes to groundwater recharge
under both current climate conditions and for the range of climate-
change scenarios for the study area.
 Use of a computer code (such as UnSat Suite or WetSpass) to estimate
groundwater recharge based on available precipitation and temperature
records and anticipated changes to these parameters.

40.  Quantify the spatially distributed recharge rates using the climate data and
spatial soil survey data.
 Development and calibration of a three-dimensional regional-scale
groundwater flow model (such as Visual MODFLOW).
 Simulate groundwater levels using each recharge data set and evaluate
the changes in groundwater levels through time.
 Undertake sensitivity analysis of the groundwater flow model.

41. A typical flow chart for various aspects of such a study is given below. The figure shows the connection from
the climate analysis, to recharge simulation, and finally to a groundwater model. Recharge is applied to a
three-dimensional groundwater flow model, which is calibrated to historical water levels. Transient
simulations are undertaken to investigate the temporal response of the aquifer system to historic and future
climate periods.

42. Hsu et al. (2007)
 Adopted a numerical modeling approach to investigate the response
of the groundwater system to climate variability to effectively manage
the groundwater resources of the Pingtung Plain in southwestern
Taiwan.
 A hydrogeological model (MODFLOW SURFACT) was constructed
based on the information from geology, hydrogeology, and
geochemistry.
 The modeling result shows decrease of available groundwater in the
stress of climate change, and the enlargement of the low-groundwater-
level area on the coast signals the deterioration of water quantity and
quality in the future.

44. Jyrkama and Sykes (2007)
 Presented a physically based methodology that can be used to characterize
both the temporal and spatial effect of climate change on groundwater
recharge. The method, based on the hydrologic model HELP3, can be used
to estimate potential groundwater recharge at the regional scale with high
spatial and temporal resolution.
 The method is used to simulate the past conditions, with 40 years of actual
weather data, and future changes in the hydrologic cycle of the Grand River
watershed. The impact of climate change is modelled by perturbing the
model input parameters using predicted changes in the regions climate.
 The overall rate of groundwater recharge is predicted to increase as a result
of climate change. The higher intensity and frequency of precipitation will
also contribute significantly to surface runoff, while global warming may
result in increased evapotranspiration rates.
 Warmer winter temperatures will reduce the extent of ground frost and shift
the spring melt from spring toward winter, allowing more water to infiltrate
into the ground.

46. CLIMATE CHANGE ADAPTATIONCLIMATE CHANGE ADAPTATION
• Managing gw. recharge
• Management of gw. storage
• Protection of gw. quality
• Managing demands for gw.
• Managing gw. discharge
Managing groundwater recharge
Protecting
groundwater
quality
Managing
demand for
groundwater
Managing groundwater
discharge
Managing
groundwater
storage
Adaptation: management responses for gw. dependent
systems to risks associated with climate variability and climate
change
• Building the adaptive capacity for groundwater

47. MANAGEMENT OF RECHARGE AND STORAGEMANAGEMENT OF RECHARGE AND STORAGE

48. CONCLUSION
 Although climate change has been widely recognized, research on
the impacts of climate change on the groundwater system is relatively
limited.
 The impact of future climatic change may be felt more severely in
developing countries such as India, whose economy is largely
dependent on agriculture and is already under stress due to current
population increase and associated demands for energy, freshwater
and food.
 If the likely consequences of future changes of groundwater
recharge, resulting from both climate and socio-economic change, are
to be assessed, hydrogeologists must increasingly work with
researchers from other disciplines, such as socio-economists,
agricultural modelers and soil scientists.

49. Thank You !!!