Integrating Raster Based GIS with Land Use, Surface Soil and Rainfall Records for the Estimation of Groundwater Recharge

Abstract:

In Taiwan, groundwater resource plays a vital role in regional water supply because the quantity of groundwater pumpage has exceeded 1/3 of the total quantity of water supply. However, without proper management of groundwater usage, series environmental impacts such as land subsidence and seawater intrusions have occurred. To achieve the goal of sustainable management of groundwater resource, an accurate estimation of groundwater recharge is required.

This study proposes to integrate PCRaster with maps of land use and surface soil and rainfall records to determine the spatial and temporal variations of groundwater recharge. PCRaster is a kind of raster based GIS software and its scripting interface is easy to create a spatio-temporal recharge estimation model. In the first step, the map of land use is re-grouped into three categories, impermeable zones, permeable zones and water bodies. For impermeable zones, the recharge quantities are assumed as zeros. Two kinds of estimating equations, a rainfall-infiltration equation and a saturated recharge equation, are respectively used to calculate the recharges of permeable zones and water bodies. The map of surface soil is used to define the spatial distribution of soil parameters in two equations. The temporal records of rainfall define the temporal variable in the rainfall-infiltration equation.

The study area is Pingtung Plain which is 1,229 km² in southern of Taiwan. In the process of estimation, the size of cells is 20 meters by 20 meters. The horizontal of estimation is during 1999 to 2010. The accumulated recharge is about 20.11 billion m³. (1.67 m³/yr). The annual recharge in 2008 is 1.89 billion m³. The annual recharges vary from 1.3 to 2.1 billion m³ because of different hydrological conditions. The infiltrated recharge in May and November in 2008 respectively are 430 (22.73%) and 67 (3.53%) million m³.