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Validation of Ex-Situ Runoff Harvesting in Semi-Arid Areas Using Grid-Based NRCS – CN

Arid and Semi-Arid agroclimatic zone covers about 80% of Kenya’s land mass and supports more than 50% of the livestock and 35% of human population. Subsistence rainfed farming is key in these areas as a source of livelihood and for food security. Cases of crop failure, under rain-fed systems, due to extra and intra season drought are rampant and currently amplified by climate change. This calls for adaptive management, water smart agricultural utilization systems, in-situ and ex situ runoff harvesting for crop production. This study aimed at validating ex-situ runoff harvesting, and the use of grid based NRCS-CN integrated with GIS tools in siting water harvesting structures and quantifying the runoff in a semi-arid zone. A multi-criteria analyses was applied to the study catchment by overlaying slope, proximity to irrigable land, soil characteristics, land use and drainage pattern. A grid-based NRCS-CN model was used to evaluate the spatial distribution of event-based rainfall excess and expected runoff volume at the selected site. The estimated volume was compared to the recorded storage volume at a water pan that was installed at selected site. Based on the multi-criteria analyses a suitable site was selected and a water pan installed with a collection ditch to direct flow to the pan. The estimated spatial rainfall excess varied between 2 mm and 7 mm for a 19.6 mm event. These reflects the potential of runoff harvesting in the area. The site selection was ground validated as runoff followed the expected pattern through the collection ditch into the water pan. The estimated event-based runoff using CN method was representative as these was reflected in recorded volume of run off harvested by the water pan. The grid based NRCS-CN integrated GIS model is proved as an effective tool for siting runoff harvesting structures and estimating the expected runoff volume.

Subsistence Rainfed Farming, Adaptive Management, Ex Situ Runoff Harvesting, Grid-Based NRCS-CN Model

APA Style

Kennedy Ochieng Okuku, Japheth Ogalo Onyando, Nancy Waithira Matheri, Samuel Muhoro Kinyanjui. (2023). Validation of Ex-Situ Runoff Harvesting in Semi-Arid Areas Using Grid-Based NRCS – CN. American Journal of Water Science and Engineering, 9(3), 77-85.

ACS Style

Kennedy Ochieng Okuku; Japheth Ogalo Onyando; Nancy Waithira Matheri; Samuel Muhoro Kinyanjui. Validation of Ex-Situ Runoff Harvesting in Semi-Arid Areas Using Grid-Based NRCS – CN. Am. J. Water Sci. Eng. 2023, 9(3), 77-85. doi: 10.11648/j.ajwse.20230903.14

AMA Style

Kennedy Ochieng Okuku, Japheth Ogalo Onyando, Nancy Waithira Matheri, Samuel Muhoro Kinyanjui. Validation of Ex-Situ Runoff Harvesting in Semi-Arid Areas Using Grid-Based NRCS – CN. Am J Water Sci Eng. 2023;9(3):77-85. doi: 10.11648/j.ajwse.20230903.14

Copyright © 2023 Authors retain the copyright of this article.
This article is an open access article distributed under the Creative Commons Attribution License ( which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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