Detecting the short term impact of soil and water conservation practices using stage as a proxy for discharge—A case-study from the Tana sub-basin, Ethiopia

Liya Weldegebriel, Mikaela Kruskopf, Sally Elizabeth Thompson, Kibret Tebeje

Research output: Contribution to journalArticle

Abstract

Efforts to tackle land degradation worldwide have spurred the adoption of soil and water conservation (SWC) practices intended to reduce surface runoff and erosion. Despite their widespread implementation, missing or incomplete monitoring remains a pervasive problem preventing evaluation of how well SWC practices meet these aims. When using runoff and sediment loss as main parameters to evaluate SWC efficacy, the key metrics are the production of flow per unit rainfall (runoff ratio), and exported sediment (sediment concentration). We develop a method to assess changes in these metrics in the absence of a flow rating curve, using more complete and reliable measurements of stage (flow depth). We apply these methods to datasets with incomplete rating curve collected from five watersheds included in the Tana and Beles Integrated Water Resource Development Project (TBIWRDP) in the Abay (Blue Nile) basin, Ethiopia. Changes in runoff ratio and sediment concentration relative to the first year of treatment varied by season. In the long wet season (Kiremt) that generates most runoff and erosion, reductions in runoff ratio and in sediment concentration occurred in four watersheds. Reductions in the runoff ratio were directly proportional to the areal density of SWC treatments in the watersheds, suggesting that SWC treatments were effective in controlling runoff and erosion.We suggest that stage and sediment concentration information can be used to assess watershed responses to SWC treatments. Focusing on these measurements, may facilitate the design of reliable and affordable monitoring programs, and ultimately facilitate improved financing approaches based on reasonable estimates of likely SWC practice performance.

Original languageEnglish
JournalLand Degradation and Development
DOIs
Publication statusE-pub ahead of print - 27 Aug 2020

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