Estimating and analyzing the spatiotemporal characteristics of crop yield loss in response to drought in the koshi river basin, Nepal

The quantitative assessment of crop yield loss due to drought is critical for the development of the agricultural sector to improve the productivity. This study aimed to estimate and analyze the spatiotemporal patterns of crop yield loss in response to drought using the Lagrange interpolation method, wavelet analysis, and sequential Mann–Kendall test in Nepal's Koshi River Basin, covering the mountain, hill, and Terai (low-land) regions from 1987 to 2016. The findings indicate that average crop yield loss was common after 2000, with the Terai, hill, and mountain regions experiencing the greatest loss in maize, rice, and wheat crops, respectively. The average annual rice and wheat yield losses rate were highest in the mountains, while maize yield losses were highest in the Terai. The mountain region experienced an abrupt change in wheat yield loss, showing a significant increasing trend. The hill region showed a significant increase in maize and wheat yield loss, while a decrement in rice yield loss was observed. The periodic variations of maize, rice, and wheat between 1987 and 2016 revealed significant yield loss after 2000. The characteristics of the first and second key periods for crop yield loss demonstrated a variation period, predicting that crop yield loss would either enter a high yield loss or low yield loss period shortly after 2016. The study findings provide a detailed assessment of crop yield loss at the river basin level, highlighting the urgent need to develop a crop yield loss mitigation plan in the agricultural sector.