Harvesting of seasonal, tidal rivers: a case study

Abstract

The present study reports harvesting of Pavanje River, a seasonal, west-flowing river of Karnataka, as a possible measure to meet the increasing domestic water demand of the basin. The present proposal envisages harvesting of river water through construction of a vented dam at a suitable location. The domestic water demand forecasted for the surrounding villages of the proposed location for the year 2026 is about 4.363 × 10⁻³ Mm³/d. Hydrological analysis carried out using river flow data for the period 1971 to 1998 is being utilised to estimate the possible storage. The analysis based on 95% daily dependable flow indicates that the river flow is less than the demand during February 15 to June 6 (i.e. for 115 days). The storage required for this deficit period is about 0.46 Mm³. Storage analysis was carried out using the mass curve and sequent peak algorithms. The storage capacity needed to satisfy the demand by the mass curve and the sequent peak methods was estimated to be 0.762 Mm³ which may be considered as the storage capacity of river water harvesting structure, that is, the vented dam. Also, the storage capacity of the proposed vented dam at the proposed site was estimated using ArcGIS, which was about 0.963 and 1.374 Mm³, respectively, for 3 and 4 m heights of the dam. The vented dam at this location also prevents saltwater intrusion into upper reaches during the period November to May. The results obtained from the investigation may lead to such river water storage structures across many tropical, seasonal rivers worldwide to cater to domestic, agricultural and other demands.

Keywords:

• river water harvesting
• saltwater intrusion
• storage capacity
• vented dam