Evaluation of Hydrometeorological Characteristics in the Northern Ethiopia, Gerado Catchment

Abstract

In Northern Ethiopia, land degradation, together with population pressure foster soil erosion. Soil erosion in turn escalates surface runoff which is a serious challenge to agricultural production and economic growth in the region. Understanding the characteristics and dynamics of hydrometeorological variables are important elements in water resources development projects. Present study was carried out to evaluate hydrometeorological characteristics in the Northern Ethiopia, Gerado Catchment. Long term meteorological data such as precipitation, temperature and other climatic factors were collected from existing meteorological stations. Thornthwaite empirical equation and thornthwaite soil water balance models were employed in estimating potential and actual evapotranspiration. The first approach used air temperature as an index of energy available for evapotranspiration. Similarly, groundwater recharge of the catchment was computed as a difference of between outflow and change in a water storage. The runoff of the area was calculated based on the rainfall coefficient, annual precipitation and aerial coverage. On the other hand, groundwater potential (GWP) of the area was mapped based on important selected controlling factors. The result indicated that the annual potential and actual evapotranspiration of the catchment was found to be 755 mm/year and 723 mm/year respectively. The actual evapotranspiration was evaluated and weighted based on the dominant soil textures, depth root soil, and the respective land uses. As result, high evapotranspiration was observed in moderate deep rooted cereal crops and sandy loam soil texture which accounted 48.5% influence. But, cereal crops with moderate deep rooted and clay loam type have low AET (42.2%). Because of absence of gauging stations in the catchment, the volume runoff was computed using the runoff coefficient method. Accordingly, surface runoff from the catchment was calculated to be 120,581,841 cubic meter (m3) or 326 mm. Whereas, the groundwater recharge of the area was also found to be 52,208,159.5 cubic meter (141.5mm). Thus, out of the given mean annual precipitation, 27.6% and 12% of the mean annual rainfall lost because of runoff and recharge and the rest (60.4%) due to evapotranspiration. Regarding GWP suitability mapping, lithology, liniment density and geomorphology were found the most essential factors affecting groundwater mapping. The suitable GWP areas were lied within lithology and geomorphology class. Moreover, areas with flat slope and low lineament density are also located in most rich groundwater areas. Furthermore, installation of rain gauges at appropriate areas are essential for all inclusive and consistent data availability. 
 Keywords: Hydro-meteorological, Gerdo Catchment, groundwater recharge, runoff, evapotranspiration, GWP