Tennant Concept Coupled with Standardized Precipitation Index for Environmental Flow Prediction from Rainfall

Abstract

By coupling the standardized precipitation index (SPI), frequently used as a meteorological drought index, with the Tennant concept, popularly used in environmental flow (EF) assessment, this paper attempts to predict the EF condition of a catchment using easily available rainfall data only, which is useful for ungauged catchments. Its application is demonstrated using the data of three catchments of the Mahanadi Basin (Ghatora, Kurubhata, and Salebhata), two catchments of the Brahmani-Baitarini Basin (Anandpur and Jaraikela), two catchments of the Godavari Basin (Hivra and Nandgaon), and four catchments of the Narmada Basin (Mohegaon, Hridaynagar, Manot, and Sher), which fall in subtropical and subhumid climatic regions of India. A coefficient of determination of more than 0.7 for most of the catchments showed the existence of a relationship between SPI and % average annual flow (AAF) (used to describe the EF condition). Therefore, the EF condition of the previously named catchments can be ascertained using SPI derived from easily available rainfall data.