水文学: 現在の研究

Severity Classification and Characterization of Waterlogged Irrigation Fields in the Fincha'a Valley Sugar Estate, Nile Basin of Western Ethiopia

Abstract

Getahun Kitila, Gizachew Kabite and Tena Alamirew

Waterlogging is becoming the major threat to the sustainability of irrigated agricultural lands in Fincha’a Valley Sugar Estate (FVSE). In the present study timely and accurate detection of waterlogged areas through piezometer monitoring and remote sensing indicators, along with their characterization and severity classification has been made. Accordingly, spatial maps of groundwater table (GWT) depth were produced in a Geographic information system (GIS) (ArcGIS 10.2) environment from 40 groundwater monitoring piezometer data. Results of the study revealed that FVSE, after nearly 20-25 years of irrigation, is experiencing a serious waterlogging problem. About 324.4 km2 (75.5%) of the delineated plantation fields are severely waterlogged and 105 km2 (24.5%) are critically waterlogged. The study also revealed that the GWT depth for all selected irrigation fields is very shallow in winter compared to spring, autumn and summer seasons. The seasonal fluctuation and spatial variability of groundwater table in the irrigated fields is owing to excess irrigation water application, nature of the soil, topography and high seepage from water bodies and poor drainage system; hence are the main causes for waterlogging (GWT rise) problem in the study area. The groundwater depth is extremely shallow (<1 m below ground) in most of the piezometer sites (about 94.7% of the study area) throughout the entire season and showed great spatio-seasonal variability. The rate of annual increment of groundwater rise, coupled with seasonal fluctuation, has obvious repercussions and grave consequences for the sustainability of Fincha’a Valley Sugar Estate. The serious problem of the rising groundwater table can be tackled by adopting improved irrigation water management practices, designing drainage system and further geological investigations. Therefore, it is highly suggested to critically study the causes, consequences and solutions of the waterlogging problem (GWT rise) in a concerted and integrated manner to get out of this vicious problem.