Estimation of the water table depth of the Calarasi district Island (Romania) at the Danube River using ASTER/DEM data

Abstract

The water table is the top level of ground water by definition. Therefore surface water is an exposed part of the water table. Airborne measurements, resistivimeters determinations or perforation analyses can be used to determine the water table depth. These methods require, approximately, taking a sample per hectare, which is a very expensive and time-consuming procedure. However, remote sensing constitutes an ideal alternative to determine water table depth, because unlike the existing methodologies, which are very expensive due to equipment and travel expenses, the proposed methodology is cheap and simple. The ASTER GDEM data is available at no charge to users via electronic download and also its resolution is appropriate to the size of the study area chosen. Using ASTER GDEM data, the water table depth of an island has been calculated. In that case, the water table depth can be approximately calculated by means of the difference between the altitude of each point in the island and the altitude of the river at that moment. In this work, an island of the Danube River, located near the Rosetti village (Calarasi district) in Romania was selected as study area and the measurements carried out by ASTER/DEM were used to obtain the water table depth. The water table depth of the island, measured on June 30, 2008, was variable between 1 and 8 m. These results were compared to a topographical map of the area made by the URSS Army Cartographic Service, drawn in a fifty thousand to one scale and dating from 1991. Finally values were validated taking some in situ samples at the island wells. An Root Mean Square Error (RMSE) of 1 m was obtained.

Keywords:

• ASTER/DEM
• island
• water table depth