Groundwater Modeling for. in the Upper Central Plain of Thailand

Transcription

1 Groundwater Modeling for Conjunctive Use Patterns Investigation in the Upper Central Plain of Thailand Colloque International Symposium May 31, 2006 Dijon, France Werapol Bejranonda Water Resources System Research Unit, Faculty of Engineering Chulalongkorn University, Bangkok Thailand

2 Study Area Methodology Contents Groundwater Modeling Conjunctive use pattern investigation

3 Research Objectives Investigate use-patterns of conjunctive water between groundwater and surface water in the upper central plain of Thailand Estimate the impact of groundwater use via the use-patterns

4 Study Area Geological Map of Thailand Upper Central GW Basin of great central basin Agricultural Bangkok (Capital) *The first upper central regional GW Model Lower Central GW Basin of great central basin Industrial Agricultural GW Basins Hydrogeological map of upper central GW basin

5 Study Area Study Area Boundary 4 Main Streams -Yom Rive -Nan River -Ping River -Sakaekrang River cover 5 main surface-water basins Surface Water

6 Study Area UTD SKT PSL 47,000 km 2 KPP PCT Project study area covers 6 Provinces

7 Existing Conjunctive Use Irrigation area Rainfed area

8 Conceptual Groundwater Model Review Conjunctive Use in study area Math-Model Design Field Investigation and Literature Review - Groundwater Levels - Hydraulics Properties - Recharge Questionnaires Calibration and Verification Surface Water Shortage GW Use Pattern Analyze Surface Water Uses Surface Water Balance Analysis Result - Irrigation Area - Surface Basins - Aquifer Types - Water Situations - Seasons Study flowchart

9 GW pumping behavior Field data collection (500 questionnaires) area crops/year season pumping/crop day/pumping hours/day irrigation 2.5 dry wet rainfed 2.0 dry wet pilot area (irrigation) 2.3 dry wet ,

10 Layer Classification Flood Deposit & Low Terrain High Terrain

11 GW Model (MODFLOW) 2 Layers Conceptual 10 km.10 km Model Upper : 320 grids Lower : 346 grids Upper Layer (Semiconfined) Lower Layer (Confined)

12 Recent Flood Plain Deposits Low Terrace Deposits High Terrace Deposits Rock Upper Layer thickness m. Lower Layer thickness m.

13 Calculation Method 1. Steady Calibration : Transient Calibration : Model Verification : Steady State for Hydraulic Conductivity Transient State 2003 for Specific Storage Verification

14 Computed vs. Observed Values Head Steady Calibration & Verification Trans. Observed Head Transient Observed Calculat ion Calibration (Steady) Calibration (Transient) Verification (Transient) Average Error (m) Root Mean Square Error(m)

15 Observed Simulation (steady) Groundwater Level in dry season of 2003

16 Surface Water Budget Situation 18,000 16,000 Bhumibol+Sirikit Reservior Storage at January 1st more 12,500 MCM : Wet Year Total reservior usable storage ( (Million m3) 14,000 12,000 10,000 8,000 6,000 4,000 6,500-12,500 MCM : Normal Year 4,000-6,500 MCM : Dry Year 2,000 less 4,000 MCM : Drought Year Year

17 Space Dimension Aquifer types pump yield M 3 /hr GW use to demand GW Use flood deposits Low terrace deposits % 7% Ratios Water situation Wet Normal water demand : SW : GW (all in dry season) 1 : 0.49 : : 0.32 : 0.36 high terrace deposits % Basin water demand : SW : GW Irrigation area rain-fed area Ping 1 : 0.54 : : 0.83 : 0.17 Yom 1 : 0.90 : : 0.87 : 0.13 Nan 1 : 0.53 : : 0.97 : 0.03 Chaophraya 1 : 1.00 : : 0.99 : 0.01 Sakaekrang 1 : 0.83 : : 0.99 : 0.01 all basins 1 : 0.62 : : 0.93 : 0.07 Dry Drought Irrigation condition irrigation area 1 : 0.47 : : 0.63 : 0.68 water demand : SW : GW (all in wet year) rainy season dry season whole year 1 : 0.74 : : 0.50 : : 0.66 : 0.13 Time Dimension rain-fed (no irrigation) 1 : 0.98 : : 0.54 : : 0.94 : 0.06

18 Water Use (Million m 3 /year) Surface Water Use Ground Water Use Surface and Groundwater Use Ratio of Groundwater Use to Total water demand (% % 35% 30% 25% 20% 15% 10% 5% Conjunctive Use Patterns Ratio of Groundwater Use to total water demand 0% Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry

19 Different GW Level from Calculation Approach (1) average pumping rate (2) 0.7% increasing pumpinge rate Groundwater Level (m MSL) gw level with conjunctive pattern approach gw level with average pumping rate approach gw level with 0.7% growth-rate approach (3) conjunctive patern Year

20 Application#1 : GW Level in pilot area Conjunctive Ratio Approach 29 Groundwater Level in Mae Nam Yom basin 27 Groundwater Level (m.msl) Agricultural well yield Groundwater Level Moving average Simulated as Drought year 12-month moving average

21 Application#2 : Regional GW table Simulated groundwater table using conjunctive use ratio

22 Conclusions Groundwater use varies on deficit of surface water supply Conjunctive use pattern significantly varies with surface water situation, season, aquifer characteristic and irrigation-rainfed rainfed area Conjunctive use pattern is a key factor to estimate groundwater consumption and simulate groundwater-level fluctuation

23 References Faculty of Engineering, Chulalongkorn University (2002), Groundwater Potential in Lower Central Part of Thailand. Koontanakulvong,, S. and Siriputtichaikul P. (2003), Groundwater Modeling In the North Part of the Lower Central Plain, Thailand, International Conference On Water and Environment, Bhopal, India, Vol.Ground Water Pollution No.19, pp Panot (2000) 2000), Groundwater Modeling of Lower Central Part of Thailand.

24 Acknowledgement Department of Groundwater Resources Royal Irrigation Department Water Resources System Research Unit, Chulalongkorn University