Evaluation of drought impact on groundwater recharge rate using SWAT and Hydrus models on an agricultural island in western Japan

G Jin,S Onodera,M Saito,K Matsumori,Y Shimizu

doi:10.5194/piahs-371-143-2015

Abstract

Abstract. Clarifying the variations of groundwater recharge response to a changing non-stationary hydrological process is important for efficiently managing groundwater resources, particularly in regions with limited precipitation that face the risk of water shortage. However, the rate of aquifer recharge is difficult to evaluate in terms of large annual-variations and frequency of flood events. In our research, we attempt to simulate related groundwater recharge processes under variable climate conditions using the SWAT Model, and validate the groundwater recharge using the Hydrus Model. The results show that annual average groundwater recharge comprised approximately 33% of total precipitation, however, larger variation was found for groundwater recharge and surface runoff compared to evapotranspiration, which fluctuated with annual precipitation variations. The annual variation of groundwater resources is shown to be related to precipitation. In spatial variations, the upstream is the main surface water discharge area; the middle and downstream areas are the main groundwater recharge areas. Validation by the Hydrus Model shows that the estimated and simulated groundwater levels are consistent in our research area. The groundwater level shows a quick response to the groundwater recharge rate. The rainfall intensity had a great impact on the changes of the groundwater level. Consequently, it was estimated that large spatial and temporal variation of the groundwater recharge rate would be affected by precipitation uncertainty in future.

Highlights

Estimation of groundwater recharge, quantity, and water balance is important for efficiently managing groundwater resources
The annual variation of the water balance is shown in Fig. 3, there shows lower values in both surface runoff and groundwater recharge in the drought year
In the low precipitation year, the groundwater recharge and surface runoff decreased to 25 and 30 %, respectively. Both river discharge and groundwater recharge fluctuated between the high and low precipitation years compared to average water balance (Fig. 3), and these variations are larger than the precipitation fluctuation

Summary

Introduction

Estimation of groundwater recharge, quantity, and water balance is important for efficiently managing groundwater resources. Former methods of groundwater recharge estimation are normally subject to large uncertainties and cause errors (Kurylyk et al, 2013). Based on this issue, computer based hydrological models could provide an option for solving this complex problem. Climate changes due to global warming may alter rainfall patterns and increase the occurrence of extreme events (floods and droughts), i.e., a change in the frequency and intensity of rainstorms (Nicholls and Hoozemans, 1996) This will increase the severity of droughts, and in past decades has caused variation and uncertainty of the regional water balance. Because climate change will significantly affect the sustainability of water supplies in the coming decades, understanding future water budgets will be necessary and important

Objectives

Results

Conclusion