Geospatial Water Quality Analysis of Dilla Town, Gadeo Zone, Ethiopia – A Case Study

Abstract:

Dilla is a socio-economically important town in Ethiopia, established on the international highway joining capital cities of Ethiopia and Kenya. It serves as an administrative center of the Gedeo Zone in SNNPR region of Ethiopia accommodating around 65000 inhabitants and also as an important trade centre for coffee. Due to the recent developments and urbanization in town and surrounding area, waste and sewage discharge has been raised significantly into the water resources. Also frequent rainfall in the region worsens the problem of water quality.

In this view, present study aims to analyze water quality profile of Dilla town using 12 physico-chemical parameters. 15 Sampling stations are identified amongst the open wells, bore wells and from surface water, which are being extensively used for drinking and other domestic purposes. Spectrophotometer is used to analyze data and Gaussian process regression is used to interpolate the same in GIS environment to represent spatial distribution of parameters. Based on observed and desirable values of parameters, water quality index (WQI); an indicator of weighted estimate of the quantities of various parameters ranging from 1 to 100, is developed in GIS. Higher value of WQI indicates better while low value indicates poor water quality. This geospatial analysis is carried out before and after rainfall to understand temporal variation with reference to rainfall which facilitates in identifying the potential zones of drinking water. WQI indicated that 8 out of 15 locations come under acceptable category indicating the suitability of water for human use, however remaining locations are unfit. For example: the water sample at main_campus_ustream_1 (site name) site has very low WQI after rainfall, making it unfit for human usage. This suggests undertaking of certain measures in town to enhance the water quality. These results are useful for town authorities to take corrective measures and ameliorate the water quality for human use.