Recipient Organization
UNIV OF HAWAII
3190 MAILE WAY
HONOLULU,HI 96822
Performing Department
NATURAL RESOURCES & ENVIRONMENTAL MANAGEMENT
Non Technical Summary
The decline in Hawaii's sugar cropping presents an opportunity for diversified agriculture to utilize plantation irrigation systems. The project will investigate the transformation of plantation irrigation systems into multi-crop and -user schemes and test possible policy reforms for water allocation and system cost recovery.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
(1) Develop a computerized mathematical model of a former plantation irrigation system and water allocation for diversified uses, calibrated for the Waiahole Ditch system on Oahu. (2) Simulate the computerized model to determine the impacts of alternative water allocation rules and irrigation system cost recovery options at the Waiahole Ditch system. (3) Adapt the irrigation model and simulation design to investigate relevant alternative(s) for other Hawaii plantation irrigation system(s).
Project Methods
(1) A nonlinear optimization model of irrigation water allocation will be specified to include the following subcomponents: objective function to maximize the net benefits from irrigation; system water supply, delivery and deep percolation; agricultural cropping, water use and yield; farm product markets and prices; nonagricultural water demand and use with alternative water sources; irrigation system costs and water pricing; water rights and allocation. Model calibration data will be collected on: diversified agriculture production costs and returns, crop water uses and yield responses, local and export markets; Waiahole Ditch water supply, irrigable lands, system costs, alternative water supply; nonagricultural water demand in cental Oahu. Empirical values of model parameters will be estimated through a variety of statistical and synthetic techniques. The empirical model will be computerized using the General Algebraic Mathemetical System software. Initial model
simulations of current conditions will be compared to the field situation, with recalibration where large divergences are detected. (2) The simulation component will have an experimental design for alternative water allocation rules (e.g., current water permits, increase in sectoral water allocations, intra- and inter-sectoral water markets) and cost recovery options for different shares of system capital, operation and maintenance costs. Calibration simulations will test model sensitivity such that the final design incorporates significant interactions. Simulation output will include: crop irrigated area, production, value added, water use and value; irrigation system costs and revenues; nonagricultural ditch water use and irrigated area. (3) Depending on the specific additional system(s) to be studied, the Waiahole model specification may be extended to accommodate multiple ditch water sources and/or the spatial distribution of water among subsystems. Collection of site-related data
on ditch water supply, operational parameters, costs, alternative water sources and potential nonagricultural demand will be necessary. Additional data and revised parameters for the water balance and crop response functions may be needed where growing conditions differ significanctly from the Waiahole case. The diversified agriculture portion of the model can be easily modified for different cropping alternatives, farm types, yields, product prices and other market conditions. The simulation design will also be adapted for physical, economic and/or policy alternatives relevant to the selected system(s).