Estimating Groundwater Recharge under Upland and Depression Using a Simple Soil Water Balance Model

Transcription

1 Estimating Groundwater Recharge under Upland and Depression Using a Simple Soil Water Balance Model Ligang Xu, Masaki Hayashi, John Jackson and Laurence R. Bentley Department of Geosciences, University of Calgary Introduction Groundwater recharge What is groundwater recharge? Precipitation Evaporation Transpiration Run off Water table Root depth Recharge Mainly controlling factors: climate, soils and geology, vegetation and land use, topography, and water table. The quantification of groundwater recharge is a prerequisite for efficient and sustainable groundwater resource management. 1

2 Introduction Groundwater recharge estimation methods How to estimate groundwater recharge? 1. Soil water balance method (soil moisture budget); 2. Zero flux plane method; 3. 0ne-dimensional soil water flow model; 4. Inverse modelling for estimation of recharge (two-dimensional ground water flow model); 5. Saturated volume fluctuation method (ground water balance); 6. Isotope techniques and solute profile techniques. From C.P. Kumar, 2004 Objectives Test and improve a water balance model for groundwater recharge estimation between the upland site and the depression site. Identify further work for watershed-scale groundwater recharge. 2

3 Study site Uplands Land use: Grass pasture : June 7-Oct. 31,2006 Depression (C24) Artificial flooding depression : June 1-Oct. 26,2004 Spy Hill Farm Instrumentation Meteorological stations Water content reflectmeter & TDR (A); Tensiometers(B) B B 10 cm 30 cm A A 60 cm Eddy covariance system 100 cm 150 cm Upland Depression 3

4 Precipitation. Conceptual model for upland Evapotranspiration Runoff Soil water balance: R p = P E S RO Upland P: Precipitaion, E: Actual evapotranspiration depends on crop growth stage, S :Daily change in moisture, RO: Run off by potential recharge rain or snowmelt, R p : Potentail recharge Model input: Land use; Precipitation; Meteorological data; Soil moisture retention; Crop coefficient; Drying curve Model output: Evaporation; Soil moisture for each layer; Rain runoff; Snowmelt runoff; SWE ; Potential recharge Comparison of volumetric soil moisture between measured values and simulated values at two soil layers at uplands Precipitation(mm) Precipitation D a t e Volumetric soil moisture(cm 3 /cm 3 ) Volumetric soil moisture(cm 3 /cm 3 ) Measured values Simulated values Measured values Simulated values 30 cm 60 cm

5 Comparison between field data and simulated data at upland 500 Total soil moisture (mm) VSMBm Field Total soil moisture Simulated AET Measured AET AET(mm/day) AET Conceptual model for depression Precipitation Evaporation Depression Snow drift, runoff Soil water balance: D=R in (Runoff + Runof) D+ D i +P PE R= S D: Runoff from upland,d i : initial depression water, P: Precipitaion, S :Daily change in moisture, PE: evaporation, R : Recharge Groundwater recharge for depression The storage capacity for each layer (Stor i ) is defined as: Stor i = Saturated water content i Soil moisture i The excess water drainage to next layer can not exceed the actual hydraulic conductivity of next layer 5

6 Results and discussion depression Volumetric soil moisture Volumetric soil moisture Simulated values Measured values Pond depth(mm) Simulated pond depth Measured pond depth Soil moisture comparison between field data and simulated data on 30 cm layer at depression Simulated and measured depression pond depth after flooding Watershed-scale groundwater recharge Three different scales of modelling groundwater recharge (a) Individual depression and upland (b) Land parcel with many depressions and uplands (c) Watershed covered by HRUs 6

7 Watershed-scale groundwater recharge Conclusion Improved water balance model estimates the major prairie hydrologic parameters reasonably. The improved water balance model is relative simple and provide a frame work to estimate the watershed scale groundwater recharge to meteorological forcing and land use change. Improved water balance model will be developed as part of an integrated surface-groundwater model for watershed-scale investigations. 7

8 Acknowledgments Funding Canadian Foundation for Climate and Atmospheric Sciences Drought Research Inititive Alberta Environment NSERC Alberta Ingenuity Centre for Water Research Environment Canada Science Horizons Program 8