Is the Indus Basin Drying?: Disparities in the Environmental Flow, Inflow, and Outflow of the Basin

Abstract

Under the 1960 Indus Water Treaty, Pakistan owned the Western rivers (Indus, Jhelum, and Chenab) and India the Eastern rivers (Ravi, Suleimanki, and Beas). Pakistan's per capita water availability will reduce from 5260 m3 to less than 1000 m3 by 2025, causing water stress. The Indus Basin's water availability was examined at inflow and outflow gauges between 1991 and 2015. The Indus Basin inflow and outflow gauges indicated exceptionally low and high flows before, during, and after floods. Lower flow values vary greatly for the Indus, Chenab, and Jhelum rivers. During Rabi and Kharif, the Indus and Chenab rivers behaved differently. Lower flows (Q90 to Q99) in Western Rivers are more periodic than higher flows (Q90 to Q99) and medium flows (Q90 to Q99). The outflow gauge Kotri reported 35% exceedance with zero flows during pre-flood and post-flood seasons and 50% during flood season, indicating seasonal concerns. Outflow and inflow both fell, particularly after the year 2000, according to data collected over a longer period (1976-2015). Low storage and regulating upstream capacity caused the Indus Basin outflow to reach 28 MAF (million acre feet) between 1976 and 2015, which is 70% more than the permitted 8.6 MAF downstream Kotri gauge. For 65 percent of the year, the Indus Basin does not release any water downstream of Kotri. As a result, the ecosystem relies on an annual influx of at least 123 MAF to sustain itself, and an outflow of 8.6 MAF from the Indus Basin necessitates an inflow of 113.51 MAF. At high-flow seasons, the Indus Basin experiences devastating floods, yet it dries out at a frightening rate before and after floods. The preservation of ecosystems and riparian zones downstream depends on the large environmental flows in eastern rivers. This is achievable only by fully implementing IWT and improving water management practices at western rivers.