Wet-environment Evapotranspiration and Precipitation Standardized Index (WEPSI) for drought assessment and monitoring

Abstract

Drought assessment and monitoring are essential for its proper management. Drought indices play a fundamental role in this. This research introduces the Wet-environment Evapotranspiration and Precipitation Standardized Index (WEPSI) for drought assessment and monitoring. WEPSI incorporates water supply and demand into the drought index calculation. WEPSI considers precipitation (P) for water supply and wet-environment evapotranspiration (ET w ) for water demand. We use an asymmetric complementary relationship to calculate ET w with actual (ET a ) and potential evapotranspiration (ET p ). WEPSI is tested in the transboundary Lempa River basin in the Central American dry corridor. ET w is estimated based on evapotranspiration data calculated using the Water Evaluation And Planning (WEAP) system hydrological model. To investigate the performance of WEPSI, we compare it with two well-known meteorological indices (Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index), together with a hydrological index (Standardized Runoff Index), in terms of statistical metrics and mutual information (MI). We compare WEPSI-derived droughts and historical information, including crop production, cereal yield, and the Oceanic Nino Index (ONI). Results show WEPSI has the highest correlation and MI, and the lowest deviation. It is consistent with the records of the crop production index, cereal yield, and the ONI. Findings show that WEPSI can be used for agricultural drought assessments.

Wet-environment Evapotranspiration and Precipitation Standardized Index (WEPSI) for drought assessment and monitoring

“…Based on basin management by local authorities and physiographic characteristics, the Lempa River basin was divided into the following eight sub-basins: Lempa 1, Lempa 2, Lempa 3, Guajillo, Suquioyo, Acelhuate, SS6, and SS3 (Figure 1). Khoshnazar et al (2021aKhoshnazar et al ( , 2021b showed that the WEAP-derived variables are reliable for drought assessment in the Lempa River basin. For the description of the validation and calibration procedure of the model, interested readers are referred to our previous publication (Khoshnazar et al 2021a(Khoshnazar et al , 2021b.…”

“…Khoshnazar et al (2021aKhoshnazar et al ( , 2021b showed that the WEAP-derived variables are reliable for drought assessment in the Lempa River basin. For the description of the validation and calibration procedure of the model, interested readers are referred to our previous publication (Khoshnazar et al 2021a(Khoshnazar et al , 2021b.…”

“…In this order, the daily datasets of wind speed (u a ), net shortwave radiation (R S, net ), and vapor concentration (c a ) for 31 years and for each sub-basin are used to calculate the monthly average of these three inputs. The meteorological data u a , R S, net , and c a were retrieved from MARN (2019a) and Khoshnazar et al (2021aKhoshnazar et al ( , 2021b. The ranges of the obtained b values are validated by comparing them with the values available in the literature (Aminzadeh et al 2016).…”

“…A drought event starts once the drought index value goes below a threshold and ends as the value rises above the threshold again (Corzo Perez et al 2011;Brito et al 2018;Corzo et al 2018;Diaz et al 2020). The threshold used in this application was drought index ¼ À1, which is a threshold commonly used in drought assessments (Diaz et al 2020;Khoshnazar et al 2021aKhoshnazar et al , 2021b.…”

“…This raises doubts about the use of P-T model outputs without calibration of its coefficient (Aminzadeh & Or 2014). Accordingly, we used an asymmetric Complementary Relationship (CR) to obtain ET w using ET a and ET p , based on our reliable data (Khoshnazar et al 2021a(Khoshnazar et al , 2021b. To evaluate the performance of WEPSI, we first compared its results with both well-known drought indices (SPI, SPEI), as well as with the Standardized Runoff Index (SRI).…”