Sustainable Groundwater Development And Management For Irrigation In Raya And Kobo Valleys Northern Ethiopia

The study focuses on the sustainability of the groundwater use for domestic and agriculturalrnpurpose in Raya and Kobo valleys. The Raya valley, which comprises of Alamata, Raya-rnAzebo, Enda-Mehoni, Ofla weredas is found in southern Tigray regional state bounded withinrnin 12° 5'-12° 58' north latitude and 39° 20' -39° 53' east longitude. The Kobo valley, whichrncomprises of Kobo wereda, is found in northern Wello of Amhara regional state bounded withrnin 11° 5' -12° 11' north latitude and 39° 22' -39° 48' east longitude. The study areas are endowedrnwith groundwater fertile land livestock and agro-climatic conditions.rnThe sustainability of the groundwater use for domestic and agricultural purpose is evaluatedrnusing indicators of groundwater importance (total groundwater abstraction / total renewablerngroundwater resource), indicators of groundwater exploitation and groundwater vulnerabilityrnindicator. To estimate the value of these indicators, the annual recharge is estimated usingrnwater balance method and chloride mass balance method. The total annual recharge estimated,rnfor Raya valley and Kobo valley, based on the former method is 129.9MCM and 85.59MCM,rnrespectively. Further, using the latter method it was estimated that 52.48mm/year for Rayarnvalley and 52.8mm/year for Kobo valley. Moreover, the total groundwater abstraction isrnestimated by computing the crops irrigation requirement using CROPWAT 8 software and perrncapita demand (20l/day) of the inhabitants that live in the valley. Water table fluctuation,rnwhich is used in the computation of exploitable groundwater resource, is estimated usingrncumulative rainfall departure method.rnIn conclusion, the current groundwater use (development) in the two valleys is sustainable andrnit is at the stage of under exploitation. In Raya valley, when the intended / proposedrnpressurized irrigation practice, which covers (26,100ha) using groundwater, is implemented,rnthe groundwater development will be reached unsustainable and moderately exploitable stage.rnThe groundwater quality of the western part of the valleys area is moderately vulnerablernwhereas the central and eastern parts of the valleys are vulnerable.rnAt the end, the current groundwater use for domestic and agricultural purpose should bernenhanced. But, when the intended/proposed agricultural practice reaches at maximumrnproduction in Raya valley, additional recharge must be implemented. To minimize therngroundwater vulnerability, proper waste disposal site must be constructed, Continuousrngroundwater quality assessments must be carried out, when fertilizer(s) is/are applied for thefarmland and vulnerability map of the areas should be prepared.

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