Evaluation of programs for regulating withdrawal of surface water under the riparian legal system

The frequency of water conflicts in riparian areas has increased in recent years, forcing water agencies to consider regulating water withdrawals from streams. In this paper, we evaluate permitting programs that would be part of such regulations. The research focuses on fixed- and fractional-flow-based permit systems, the former of which allows a constant volume of withdrawal similar to the practice in appropriative areas; the latter of which allows water abstractions proportional to streamflow. The evaluation is undertaken with respect to three performance criteria: Low flow frequency, users' net benefit, and withdrawal interruption frequency. It is concluded that the fixed-flow-based permit program is able to provide a high net benefit but causes frequent minimum streamflow violations and withdrawal interruption due to its relatively simple withdrawal formula. The fractional-flow-based permit program is found to achieve a better tradeoff in preserving the natural flow regime, the net economic benefit, and convenience to water users and administrators.