Yogyakarta coastal aquifer


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Yogyakarta coastal aquifer

  1. 1. Geological Engineering Department Faculty of Engineering Gadjah Mada University Coastal Aquifer Groundwater Modeling in the Southern Part of Yogyakarta Area Presenter Main Advisor Co-Advisor : Mr. Doung Ratha : Dr. Doni Prakasa Eka Putra : Dr. Ir. Heru Hendrayana Thesis Final Exam August 24, 2012 1
  2. 2. Agenda 1. 2. 3. 4. 5. 6. 7. Introduction Literature Review Research Methodology Characteristics of Research Area Data Analysis and Evaluation Model Application and Discussion Conclustion 2
  3. 3. 1. Introduction    Background Research Objectives Scope of Research Area 3
  4. 4. Introduction  Background The research has been conducted in Coastal Zone of the southern part of Yogyakarta Area. People in reseach area are mainly use fresh water from dug wells that abstracted from groundwater for thire daily needs (deomestics and agrigculture) Increasing of (population+agriculture) => increasing of groundwater abstraction => Degradation groundwater resources both in quantity & quality (Subsidence, Seawater Intrusion…) 4
  5. 5. Introduction  Objectives of Research The core objective of this research is to apply groundwater model flow to support groundwater management and solve such problems in study area in order to achieve 2 main objectives: 1. To understand the groundwater system which include hydrogeological conditions, groundwater flow pattern, and the system of aquifer BY:  Simulate groundwater flow flow system  Understand groundwater balance in study area  Understand hydraulic interaction between river and groundwater 5
  6. 6. Introduction  Objectives of Research (cont’d) 2. To predict and assess salt groundwater in study area BY:  Estimate the present, offshore location of the interface in the system  Assess if the interface system was stable prior to pumping  Determine the potential for intrusion or accelerated intrusion based on current pumping or future projected pumping  Estimate the impacts of abstraction when the specific well locations in study area increase abstraction rate or abstraction time 6
  7. 7. Introduction  Scope of Research area Research Located in the Parantritis Beach, Southern part of Yogyakarta area, bounded by Opak River at West and Indain Ocean at South, and Tertiary Limstone Rock at the East. Source: google earth, 2011 source: Google Earth (2011) 7
  8. 8. Introduction  Scope of Research area (cont’d) Landuse Map of Study Area The surface of research area is approximately 9.46 km² which is occopied 10 different landuse. 8
  9. 9. 2. Literature Review  Background theory  Previous research  Hypothesis 9
  10. 10. Literature Review  Background theory • Groundwater modeling • Groundwater in Coastal Aquifer      Coastal Aquifer Hydrogeology Causes of Seawater Intrusion Classification of Saline Water Types of Seawater Intrusion Estimate Seawater Interface 10
  11. 11. Literature Review • Groundwater Modeling Definition o Groundwater models is the valuable tools for management of groundwater resources which are represented of the reality of natural system and can be used to monitoring, evaluating and forecasting groundwater flow and transport.
  12. 12. Literature Review • Coastal Aquifer o In most coastal aquifer systems groundwater flows naturally towards the sea driven by the head potential created by inland recharge. o Freshwater flow influences salinity stratification
  13. 13. Literature Review • Types of Seawater Intrusion Two types of seawater intrusions 1. Lateral encroachement from the ocean due to excessive water withdrawals from coastal aquifer
  14. 14. Literature Review Types of Seawater Intrusion (con’d) 2. Upward movement form deeper saline zones due to upconing near coastal discharge/pumping wells
  15. 15. Literature Review  Previous Researches Regional Geology & Hydrogeology  Wates Formation  Sand Dunes Formation 15
  16. 16. Literature Review Regional Geology Study Area  Referring to MacDonald & Partners (1984), study area located in Wate Formation and Sand Dunes Geology. 16
  17. 17. Literature Review Wates Formation  Consist of littoral sand and gravel  Thicknes range up to 30m  Classified as minor aquifer which limited the permeability and storage (provided well yield that can support potable supplied, but only limited irrigation or industrial supplies) [Mac Donald and Partners, 1984] 17
  18. 18. Literature Review Sand Dunes Formation  Consist of fine to medium gravel & sands overlying the Wates Formation.  Thickness ranges up to 42m  It is unconfined aquifer  Groundwater elevation 3.50 to 5.60m  Depth to groundwater table 0.50 to 4.15m [Mac Donald and Partners, 1984] 18
  19. 19. Literature Review  Hypothesis 1. Aquifer in study area is unconfined with groundwater flow directions are dominantly oriented from the north of the hilly area seaward to the south. Depth of groundwater table is shallow, and material of aquifer composts of Sand varied from fine to coarse size and Gravels. Groundwater quantity is defined as minor aquifer which is limited the permeability and storativity 2. Groundwater beneath the study area is contaminated by seawater intrusion resulting from development of groundwater abstraction for the need of agriculture aspect and development of tourism sector. 19
  20. 20. 3. Research Methodology  Flow Chat of Research Methodology  Flow Chat of Modeling Process 20
  21. 21. Research Methodology Problems Definition Flow Chat of Research Methodology Desk Study Secondary Data Literature Review -Topographic map - Land use map - Regional geological map - Hydrogeological data - Meteorological data - Existing borehole data - Background study - Previous study Hypothesis Model Preparation & Running Field Reconnaissance StudyArea Determination: - Topographical observation - Landuse surveying Work Plan Model Result Application Detail Field Works Parameter Measurements Hydrogeology Dug well location  Water table measurement Pumping test Hydrology Model Calibration Soils Sampling Permeability  Rainfall data Porosity  Runoff Conclusion & Recommendation Texture Evapotranspiration  Distance of saline water interface Transmissivity and hydraulic conductivity Data Imput Optimization 21
  22. 22. Research Methodology Flow Chat of Groundwater Modeling Process Define Purpose Preparation & collection Data Understanding Natural System Develop Conceptual Model NO NO Model Calibration & Validation Sensitivity Analysis Prepare Numerical Model & Running YES Analysis Flow Model Error & Verification YES Simulation Flow Modlel 22
  23. 23. 4. Characteristics of Research Area  Hydrological Condition  Hydrogeological Condition  Groundwater Usage  Groundwater Qualilty 23
  24. 24. Characteristic of Research Area  Hydrological Condition Rainfall data were obtained from station of meteorology Bantul during 11 years => Average annual rainfall (Pundong Station) = 1855.2 mm/year =>Average monthly rainfall (Pundong Station) = 154.6 mm =>Average temperature = 25.9 (c) 24
  25. 25. Characteristic of Research Area  Hydrological Condition => Evapotranspiration = 1330.8 mm/year ; A = 9.46 km2 => Runoff = 310.5 mm/year => Groundwater infiltration = 214 mm/year 25
  26. 26. Characteristic of Research Area  Hydrogeological Condition Hydrogeological Cross Section of Study Area Based on geological map of Yogyakarta Province (scale: 1: 100 000) and some of relevant studied the thickness of aquifer in study is approcimatly ranged from 30 to 40m 26
  27. 27. Characteristic of Research Area  Hydrogeological Condition (cont’d) Groundwater Flow Pattern of Study Area Groundwater Table Measurement: 196 dug wells area measured. The depth of GW varied from 0.5 to 5 m. 27
  28. 28. Characteristic of Research Area River Measurement: There are 5 locations of river measurement were conducted to identify: River stage, River Bed, River width, and Thickness of sediment. Cross Section of River in point of measurement 28
  29. 29. Characteristic of Research Area  Hydraulic Conductivity The value of hydraulic conductivity of study are determined based on Method Stug Test of Hvorslev (1951): 29
  30. 30. Characteristic of Research Area  Hydraulic Conductivity (con’t) 30
  31. 31. Characteristic of Research Area  Hydraulic Conductivity (con’t) 31
  32. 32. Characteristic of Research Area  Groundwater Usage (cont’d) Population Growth: The growth of population could be calculated by logistic equation or Verhulst (1847) => Nt = 9 041 x e ^ (0.0187 x 2) = 9 386 person Groundwater Usage: Could be calculated by: => Vt = 9 386 person x 150 L/person/day = 1 407 831 L/day = 513 859 m3/a 32
  33. 33. Characteristic of Research Area  Groundwater Quality (salinity) The salinity of sall water in study area has been determined by the value of TDS 33
  34. 34. Characteristic of Research Area  Possibility of saltwater intrusion 34
  35. 35. 5. Data Analyis and Evaluation 35
  36. 36. Natural System Conceptual Model 36
  37. 37. Data Analysis and Evaluation Parameters Input Groundwater Recharge = 213.9 mm/year - Evapotranspiration = 1330.8 mm/year - - Hydraulic Conductivity (KX= KY = K; KZ = 0.1K) •K1 •K2 •K3 - = 1.794 E-3 m/s = 1.337 E-3 m/s = 8. 974 E-4 m/s Observed wells : 196 wells Discretization (30 x 30 m) - Model Boundaries ( Constand head, River, and No flow) - 37
  38. 38. Uncalibrated Model Result Data Analysis and Evaluation Calculated GW table vs. measured GW table 38
  39. 39. Calibrated Model Result Data Analysis and Evaluation Calibrated GW table vs. measured GW table 39
  40. 40. Groundwater Mass Balance Data Analysis and Evaluation 40
  41. 41. Data Analysis and Evaluation Groundwater Flow Model Result Groundwater Flow Pattern of Model Calculation 41
  42. 42. Data Analysis and Evaluation  Parameter sensitivity analysis (PSA) The aim of sensitivity analysis is to estimate the rate of change in the output of a model with respect to changes in model inputs. To test the thickness of aquifer within the research whether is it correct or not 42
  43. 43. Data Analysis and Evaluation  Parameter sensitivity analysis (PSA) Groundwater equipotential line recharge variation Groundwater equipotential line of Hydraulic variation => Hydraulic parameter more sensitive than recharge 43
  44. 44. Data Analysis and Evaluation  Parameter sensitivity analysis (PSA) Equipotential line of PSA 9 (10-20m) PSA10 (20-30m) , PSA11 (40-50m) are quite far from EPL of model result (30-40m) => Aquifer thickness varied from 3040m is assumed correctly. 44
  45. 45. 6. Model Application and Discustion  Application Groundwater Model to Indentify the Decreasing of Groundwater Table  Application Groundwater Model for Seawater Intrusion 45
  46. 46. Model Application and Discustion  Application GW Model to Indentity the Decreasing of WT This application is used the model result to predict decreasing of WT in the study area in next 5 and 10 years. 46
  47. 47. Model Application and Discustion Changing of GW table in Case 1 and 2 of Prediction 47
  48. 48. Model Application and Discustion  Application GW Model for Seawater Intrusion Intrusion of seawater is identified by calculating the position of seawater interface by using the priciple of Ghijben-Herzberg and also the formulation of lateral encroachment 48
  49. 49. Model Application and Discustion 49
  50. 50. 6. Conclusion 50
  51. 51. Conclusion and Recommendation  Conclusion -Based on observation head, the maximum head equaled to 5m while the minimum head equaled to 0.5m. Hydraulic gradient is estimated equaled to 2.45. Therefore, depth of groundwater within the study area is shallow and groundwater direction in research area oriented from the north to the south. -The results of parameter sensitivity of aquifer thickness 30 to 40m presented the lowest error than other cases, we can conclude that the thickness of aquifer equaled to 30 to 40m is assumed correcly. -Based on the value of hydraulic conductivity in three locations within the research area that have been calculated by Slug Test Method equaled to 1.794 10-3, 1.337 10-3, and 8.974 10-4 m/s represented sand and fine gravel material. Hence, the composition of aquifer in research area is surly sand and fine gravel 51
  52. 52. Conclusion and Recommendation  Conclusion (con’t) -The initial of saltwater interface presented beneath the study area with the maximum length of protrusion equaled to 205.1m horizontally and equaled to 40m vertically from land surface. - From the application of groundwater modeling shown that water table can be dropped down due to the increasing of groundwater usage. However, this changing is not relatively different from steady-state condition because rate of groundwater abstraction still low compare to abundance of groundwater resources in this area. The rate of groundwater abstraction is limited due to the population density is low as well as human activities such as industrial factories, hotels, and guesthouse still low this area. 52
  53. 53. Thanks for your kind attention 53