1. Surface Water and Groundwater Interaction Modelling Water Resources System Research Unit, Chulalongkorn University, Thailand Department of Geotechnology and Geohydraulics, University of Kassel, Germany Werapol Bejranonda Prof. Manfred Koch Assoc.Prof. Sucharit Koontanakulvong

2. 2 Contents Contents  Introduction  Study Area  Application  Methodology  Modeling  Results

3. Introduction study area

4. Source: RID 3 rd regional bureau Existing irrigation projects and its supplies by reservoirs Nan river Yom river Study area

5. Sukkhothai Phichit Phitsanulok Division 1 Division 2 Division 3 Thailand Study area : Plaichumpol Irrigation Project

6. Introduction study approach

7. Overview of SW-GW interaction Saturated Zone GW Pumping River/Canal Surface water Rainfall Irrigation supply

8. Objectives focused on water use and allocation in an irrigation area from both canals and local shallow wells. study water use patterns and interaction between surface water and groundwater determining the potential of conjunctive use

9. Application methodology

10. 1 2 Data collection (SW-GW) Existing monitoring well : 35 wells New-installed well : 2 wells (to investigate stream-groundwater interaction) Groundwater Level Monitoring Infiltration Test 10 points varied with soil types (to investigate surface recharge) Stream Stages

11. Over view of field data collection Canal Stage (at check gate) Saturated Zone Observed Wells Bed Materials Infiltration Test 50 m.200 m.

12. Application GW modeling

13. Upper aquifer - Semi- confined Lower aquifer – Confined 200-300 m. 40-100 m. Upper aquifer (Qfd and Qlt) Lower aquifer (Qht) Conceptual Model

14. MODFLOW 500 m. x 200 m. grid-cells

15. 1993 2005 2035 Model calibration GW potential investigatio n Calibration& Verification GW potential Investigation Demand projection GW use variation obs. gw level during simulation

16. GW Model Boundaries and Sources/Sinks River Source/Sink Head Boundaries Head Source/Sink (Pond) Flow Boundaries

17. GW Model Boundaries and Sources/Sinks Head Boundaries Flow Boundaries River Sources

18. GW table away from Main Irriagtation Cannal distance form main irrigation canal (km) main irrigation canal

19. Application results

20. Upper Aquifer (Δstorage = -34.6 ) 103.6 Lateral outflow 69.8 Lateral inflow 0.004 Leak to lower aquifers 9.2 GW pump 1.3 River-Aquifer interaction 7.1 Recharge Upper Aquifer (Δstorage = -3.3 ) 10.9 Lateral out flow 18.4 Lateral inflow 0.001 Leak from lower aquifers 13.2 GW pump Unit : million m 3 /month 1.6 River-Aquifer interact. 0.9 Recharge Dry season Wet season

21. Sukkhothai Phichit Phitsanulok Division 1 Division 2 Division 3 irrigation division gw use 2007 (mil.m 3 /year) gw potential (mil.m 3 /year) use/potential 125.241.960% 260.6221.527% 357.266.486% Total143.1329.843% water situation amount (million cubic meter)percentage to irrigation demand Irrigation demand act. surface water supply groundw. extraction planed demand act. surface water supply groundw. extraction wet27513574100%49%27% normal2688696100%32%36% dry300141156100%47%52% drought266167181100%63%68% Groundwater potential Average conjunctive water use and their ratios during the dry season

22.  guideline for conjunctive-use planning in case of normal water situation at the Plaichumpol Irrigation Project non- irrigation 0 – 25 % 25 – 50 % 50 – 140 % groundwater use ratio (percentage of irrigation supply) rive r Irrigatio n canal

23. Computed groundwater level varied with season in 1997-2007 PCP-12 PCP-19 main irrigation canal PCP-01

24. Questions & Answers 06/12/5824