Spatiotemporal Distribution Analysis of Rainfall in the Harirud-Murghab River Basin, Afghanistan

The execution of hydrological, climatological, agricultural, and development projects fre-quently encounters a key challenge: missing rainfall data at specific locations. This limita-tion can be addressed using various spatial interpolation techniques, including Spline, In-verse Distance Weighted (IDW), Kriging, and the widely used Thiessen Polygon method. The primary objectives of this study were: 1) to estimate the annual mean precipitation in the Harirud-Murghab River Basin (HMRB) in Afghanistan for the period 1979–2023; and 2) to evaluate and compare the accuracy of different spatial interpolation and average precipi-tation estimation methods in the region. For this purpose, 45 years of precipitation data from 11 hydrometeorological stations within the basin were employed. The methods tested in-cluded the Arithmetic Mean, Thiessen Polygons, and Isohyetal Lines generated through Kriging, IDW, and Spline techniques. The Root Mean Square Error (RMSE) was used to evaluate the performance of each method. The results revealed that Kriging produced the highest accuracy and the lowest error (RMSE = 18.74 mm), making it the most suitable method for estimating spatially averaged precipitation in the HMRB. The IDW, Thiessen Polygon, and Spline methods followed with RMSE values of 19.07, 19.21, and 19.56 mm, respectively. Although the differences in mean values were not statistically significant, the Kriging-based isohyetal map produced the most accurate estimate of 240.75 mm. Therefore, Kriging is recommended as the preferred technique for estimating both rainfall and solid precipitation (snow) in this basin. The study’s findings are expected to support climate anal-ysis, water resource modeling, and flood forecasting in the region.