Abstract
To improve simulation accuracy of river discharge and to quantify the hydrological cycle in irrigation-dominant basins, we developed a reservoir operation model and a water allocation and management model, and combined them to a water circulation model incorporating paddy irrigation schemes. Paddy field irrigation uses large amounts of water in monsoon Asia. River flow regulation through impoundments and diversions with large reservoirs strongly influences water circulation in river basins. Therefore, considering various water management processes for reservoirs, diversion weirs, irrigation canals, and paddy plots is crucially important for accurate estimation of river flows and for elucidation of regional hydrological cycles. To verify the simulation accuracies of water management processes and river discharges, we applied the developed model to the Mun River Basin in northeastern Thailand, which has many irrigation projects. Results revealed the following: 1) The water allocation and management model precisely represents seasonal fluctuations in the amount of water withdrawals at diversion weirs and at paddies, which depend on paddy water requirements. 2) The reservoir operation model reproduces water management during the rainy seasons and the release of irrigation water in response to water requirements during dry seasons. 3) Modeling of water management in reservoir irrigation improves the simulation accuracy of river discharge in dry seasons when the water release from reservoirs is dominant in river flows.
