Development and evaluation of an agricultural drought index by harnessing soil moisture and weather data

Authors: AJAZ, ALI - Oklahoma State University; TAGHVAEIAN, SALEH - Oklahoma State University; KHAND, KUL - Oklahoma State University; Gowda, Prasanna; Moorhead, Jerry

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2019
Publication Date: 7/4/2019
Citation: Ajaz, A., Taghvaeian, S., Khand, K., Gowda, P.H., Moorhead, J.E. 2019. Development and evaluation of an agricultural drought index by harnessing soil moisture and weather data. Water. 11(7):1375. https://doi.org/10.3390/w11071375.
DOI: https://doi.org/10.3390/w11071375

Interpretive Summary: Drought events occur frequently in the Southern Great Plains, negatively impacting the agricultural production and sustainability. This is mainly due to the fact that surface water resources in this region are scarce and vulnerable to drought. Planning and managing of limited agricultural water resources for sustainable agricultural production in the region require innovative approaches to improve drought monitoring and assessment. In this study, two new drought indices: (1) Soil Moisture Evapotranspiration Index (SMEI) and Drought Duration Index (DDI) were developed using daily soil moisture and weather data for agricultural drought monitoring in Oklahoma. Correlation analysis indicated that their performance were similar to existing similar indices in the literature. However, the SMEI was more strongly correlated with meteorological indices than existing soil moisture indices and showed similar or better performance in capturing temporal variations in magnitude of droughts. Overall, the new indices are found to be capable of capturing spatial variability in drought across Oklahoma.

Technical Abstract: Two new drought indices for monitoring agricultural drought were developed based on daily soil moisture and weather data collected at five locations across Oklahoma, representing different climates. The first index was the Soil Moisture Evapotranspiration Index (SMEI), which estimates the departure of aggregated root zone moisture from reference evapotranspiration. The second index was the Drought Duration Index (DDI), which uses a soil moisture threshold for optimum crop production to identify the portion of drought periods in each month. Correlation analysis was performed among new indices and several existing soil moisture based (SM) and meteorological drought indices. The new indices showed good agreement with existing SM indices. The average correlation coefficients were 0.65 and 0.61 for SMEI and DDI, respectively. In addition, the SMEI was more strongly correlated with meteorological indices than existing SM indices. For existing SM indices, the correlations with meteorological indices found in this study were similar to those reported in previous studies. In terms of sensitivity and response to temporal variations in drought magnitude, the SMEI had similar or better performance compared to other indices. This index was also capable of capturing the spatial pattern of drought variability across Oklahoma.