Water Balance and Groundwater Quality of Koraro Area, Tigray, Northern Ethiopia

Abstract

Achieving the Millennium Development Goals (MDG) has been given a paramount importance by both Regional and Federal Governments in Ethiopia. In this direction some stations in Hawzen Woreda, Tigray Regional state, extremely poor, have been selected as model areas to test the achievement of the MDG. This paper focuses Koraro Tabia (or Station), one of the millennium villages where shortage and bad quality water is a challenge. Water balance and the hydro chemical characteristics of groundwater have been investigated in order to assess the water potential and quality in the area. Hydrometeorological information has been used to calculate water balance parameters and the recharge amount. Accordingly, the mean annual rainfall, actual evapotranspiration, bare land evaporation, runoff and groundwater recharge was found to be 548.5 mm, 431.3 mm, 372 mm, 71.33mm and 56.7mm respectively. Twelve water samples were collected from hand dug wells and springs located in different lithologies and were tested for major anions, cations, and some trace metals in Ethiopian Geological Surveys Central Geological Laboratory. Mean electrical conductivity of water samples from different sources varies significantly. The mean electrical conductivity for the hand dug wells is found to be 5170 µS/cm and that of springs is 209 µS/cm. Piper diagram revealed that groundwater in the hand dug wells is of sodium sulfate type and spring water are calcium bicarbonate type. The results indicate that groundwater from the hand dug wells is of very poor quality with high salinity and sulfate content and does not fit for human consumption. Therefore, it is recommended to avoid water for drinking purpose from hand dug wells constructed in shale dominated areas and in the alluvial deposits underlain by shale. Moreover, groundwater recharge is also insufficient in the area due to the impervious shale unit. Hence, an adaptive management method is suggested for efficient use of water and a mechanism to isolate the bad quality water while trying to construct water supply scheme for drinking in the area.

Key words: Groundwater, Water balance, Water quality, Koraro, Ethiopia.