Hydrological Effects of Agricultural Water Supplies on Paddy Fields using Surface–Groundwater Integrated Model

Sanghyun Park,Deokhwan Kim,Hyeonjun Kim,Choelhee Jang

doi:10.3390/w14030460

Abstract

Agricultural water demands are mainly dependent on the supply from groundwater withdrawals and the supply from agricultural reservoirs. To understand the water cycle of the agricultural catchment, it is necessary to consider the actual situation of the water cycle of paddy fields in catchments through accurate hydrological modeling. In this study, streamflow simulations were implemented in consideration of the levee height of paddy fields and the irrigation period for one sub-catchment of the Boryeong Dam catchment using the integrated surface–groundwater model, CAT (Catchment Hydrologic Cycle Assessment Tool). To consider the agricultural reservoirs in modeling, the catchment was divided into the reservoir sub-catchments, upstream sub-catchments, downstream sub-catchments, and irrigated districts of each sub-catchment. This study aims to analyze the hydrological effects of agricultural reservoirs and groundwater pumping on the hydrological cycle of the catchment and on the soil moisture and groundwater level. As a result of the simulations, we found that the direct flow, baseflow, and groundwater recharge of the catchment increased with the agricultural reservoir supply water. In addition, the effect of drought on soil moisture content and groundwater level in the irrigated paddy fields from agricultural reservoirs was evaluated. The soil moisture increased by about 10% according to the water supply of agricultural reservoirs. The groundwater level rapidly decreased due to the groundwater abstraction during the irrigation period; however, it was analyzed that the water supply from agricultural reservoirs is significantly effective in preventing the decrease in the groundwater level in the irrigation season.

Highlights

Rice paddies in monsoon Asian regions account for 87% of the global paddy rice harvested area and 90% of rice production [1]
The sources of water supply for agricultural activities can be divided into agricultural reservoirs and groundwater pumping
Agricultural water supply is an essential resource for agricultural water consumption, accounting for more than 50% of the total water resource consumption, and it is highly dependent on the water supply of agricultural reservoirs [5]

Summary

Introduction

Rice paddies in monsoon Asian regions account for 87% of the global paddy rice harvested area and 90% of rice production [1]. The sources of water supply for agricultural activities can be divided into agricultural reservoirs and groundwater pumping. Water shortages due to the excessive pumping of groundwater in rural areas cause water problems for domestic consumption and can cause a shortage of water needed for agricultural activities, affecting the amount of streamflow in a catchment [4]. Agricultural water supply is an essential resource for agricultural water consumption, accounting for more than 50% of the total water resource consumption, and it is highly dependent on the water supply of agricultural reservoirs [5]. As 65% of Korean land is composed of mountainous areas and the river slopes are steep, runoff occurs in a short period, with a low flow rate during the dry season.

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