261 / 2024-02-28 19:11:35

Evaluation method and its application study of agricultural drought based on the modified Crop Moisture Index

Crop Moisture Index; agricultural drought; relative soil moisture; irrigation; Haihe River Basin

Irrigation was an important factor affecting the development of agricultural drought, but it had not been taken into account in the Crop Moisture Index (CMI), which led to a large deviation in drought monitoring. In this work, the water balance equation in the CMI was revised by an irrigation threshold method, crop coefficient and water stress coefficient based on the principle of CMI. And an evaluation method of agricultural drought based on the modified CMI was proposed. The two CMI indices were used to describe the dry-wet replacement process in the Haihe River Basin during 1993~2012, and the results of simulated soil moisture values and drought judgement right rates were compared from yearly, monthly and weekly scales by referring to the real drought conditions based on the measured soil moisture data. Finally, the spatial characteristics of the drought transition process based on the two CMI indices in the basin in 2002 were provided for performance comparison. The results of comparative analyses were as follows: (1) The relative errors of the modified soil water balance equation were smaller than those of the original equation at different time scales. The annual average relative error of the modified soil water balance equation was 5.1%, while that of the original equation was 26.2%, which was significantly higher than that of the modified equation. (2) The drought judgement right rates of the modified CMI index were higher than those of the original CMI index at different time scales. The annual judgement right rate of the original CMI index was 52.2%, but that of the modified CMI index was 61.9%, which was 9.7% higher than that of the original CMI index. Therefore, the modified CMI index not only effectively improved the accuracy of soil moisture simulation results, but also had higher monitoring accuracy of agricultural drought, which had obvious advantages in drought assessment in the large-scale irrigated farming areas. This work was of great significance to guide drought prevention and risk management in large-scale agricultural areas.