Sand Dam Suitability Assessment Using Integrated Geospatial and Multi-Criteria Decision Analysis to Strengthen Water Security in Arid and Semi-Arid Regions: A Case of the Lower Awash Basin, Ethiopia

Water security is a crucial issue in arid and semi-arid regions like the Lower Awash Basin, Ethiopia, where increasing population and economic development put pressure on limited water resources. This study evaluates the suitability of sand dam sites using a multi-criteria evaluation approach combined with geospatial techniques. Meteorological data were carefully tested for consistency and homogeneity through double mass curves, Pettitt’s test, and Mann-Kendall analysis. Key biophysical factors such as slope, stream order, soil type, land use/land cover (LULC), runoff depth, and proximity to roads were reclassified and weighted according to their importance for sand dam feasibility. Runoff depths ranged from 682-934 mm, with 69% of the basin receiving 820-930 mm, indicating abundant water availability. Slope analysis showed that 47.4% of the land has gentle gradients (0–5.23°), suitable for dam stability. However, limited feasibility was observed due to stream networks, with only 4.78% of the basin being moderately or highly suitable. Soil assessment identified Fluvisols (21.91%) and Regosols (2.5%) as ideal, whereas Leptosols (43.06%) were unsuitable. LULC mapping revealed that rangelands dominate (71.6%) and provide moderate suitability, while water bodies and flooded vegetation (~2.3%) are highly favorable. Areas more than 4,000 meters from roads (79.6%) were considered optimal to reduce flooding risks near infrastructure. Overall, the integrated analysis found only 1.2% (36,855 ha) of the basin as highly suitable and 10.96% as moderately suitable for sand dam construction, while 47.74% was unsuitable. Results show limited ideal sites and stress the need for localized assessments to ensure sustainable sand dam development.水资源安全是埃塞俄比亚阿瓦什河下游流域等干旱半干旱地区的关键议题，当地持续增长的人口与经济发展给本就有限的水资源带来了沉重压力。本研究结合地理空间技术（geospatial techniques）与多准则评价方法，对沙坝选址适宜性展开评估。研究通过双质量曲线（double mass curves）、佩蒂特检验（Pettitt’s test）以及曼-肯德尔分析（Mann-Kendall analysis），对气象数据的一致性与同质性进行了严格校验。研究依据沙坝可行性的关键影响权重，对坡度、河流水系等级（stream order）、土壤类型、土地利用/土地覆被（land use/land cover, LULC）、径流深度（runoff depth）以及道路邻近性等核心生物物理因子（biophysical factors）进行了重分类与权重赋值。流域径流深度介于682至934毫米之间，其中69%的区域径流深度处于820至930毫米区间，表明区域水资源供给较为充足。坡度分析结果显示，47.4%的区域坡度平缓（0°至5.23°），有利于沙坝结构稳定。但受河流水系分布限制，适宜区域占比偏低，流域内仅4.78%的区域具备中等或高度适宜性。土壤评估结果显示，冲积土（Fluvisols，占比21.91%）与新成土（Regosols，占比2.5%）为理想土壤类型，而粗骨土（Leptosols，占比43.06%）则不适宜沙坝建设。土地利用/土地覆被（LULC）制图结果表明，71.6%的区域为牧草地，仅具备中等适宜性；而水体与淹水植被区域占比约2.3%，为高度适宜区域。距离道路4000米以上的区域占比79.6%，该类区域被视为最优选址，可降低基础设施周边的洪水风险。综合分析结果显示，流域内仅1.2%（36855公顷）的区域为高度适宜沙坝建设，10.96%为中等适宜区域，另有47.74%的区域不适宜建设沙坝。本研究结果显示理想沙坝选址十分有限，强调需开展本地化评估以保障沙坝建设的可持续性。