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

Introduction study area

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

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

Introduction study approach

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

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

Application methodology

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

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

Application GW modeling

Upper aquifer - Semi- confined Lower aquifer – Confined m m. Upper aquifer (Qfd and Qlt) Lower aquifer (Qht) Conceptual Model

MODFLOW 500 m. x 200 m. grid-cells

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

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

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

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

Application results

Upper Aquifer (Δstorage = ) Lateral outflow 69.8 Lateral inflow 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 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

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 % % % Total % 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 wet %49%27% normal %32%36% dry %47%52% drought %63%68% Groundwater potential Average conjunctive water use and their ratios during the dry season

 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

Computed groundwater level varied with season in PCP-12 PCP-19 main irrigation canal PCP-01

Questions & Answers 06/12/5824