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Traditional delivery of water to farmers in the Maduru Oya river basin in Sri Lanka is based on seasonal reservoir releases into diversion canals and distribution canals that gravity-feed the farms. Usually water delivery schedules for the main canal are decided by the Mahaweli Authority. These schedules do not give incentives for the farmers to save water, or make improvements to delivery system efficiency. This paper describes a computer based water-quota system that relies on SMS (text) messages sent by the farmers requesting water, and a computer based water delivery system that calculates hydraulic structure gate openings for the water managers. As the first step, an unsteady flow model is developed based on the solution of the St Venants equations to analyze the hydraulics in the canal. Hydraulic transients due to inflow and outflow gate operations are investigated using this model. The results are used to develop a simple operational model for the canal system that can calculate the gate openings necessary for quota based water deliveries. The project makes use of recent advances in information technology (IT) and cheapening of computational capabilities to assist water management and farm water delivery.

Determining the spatial and temporal discretization is an important part of setting up a model. As a general rule for numerical models, the discretization has to be fine enough to show most of the details of the solution, but at the same time, it cannot be too fine to prevent excessive demand for run time and computer resources. In this paper, analytical expressions are obtained for optimal mesh size using the physical parameters of the governing ipartial differential equation (PDE), space and time scales under investigation, and run time constraints. The paper describes how sensitive the discretization is to each of the attributes around the optimum.

Calibration of integrated hydrologic models of managed systems just using historical data is a difficult task because these systems have a large number of structures and pumps operated by multiple government agencies, utilities and the public based on a variety of rules and guidelines that change over time. The operations of the facilities are too complex and unrecorded at times. Water level and discharge data collected for such managed systems with mixed urban-agricultural-natural land use types often contain unrecorded local effects that are considered as errors if the model is not intended to simulate it. Data collected for such systems have a high level of noise that cannot be easily traced to the source. A method is proposed in the paper to solve the problem of the calibration of such systems by using the existing pumps and structures to generate specific identifiable hydraulic signatures in the system that also have analytical solutions. If data related to causal stress and the resulting hydraulic signal are collected free of noise, they can be used to calculate parameters directly using analytical methods or optimization methods. The paper describes such a test carried out in South Florida, and the use of an analytical method to obtain the parameters. INTRODUCTION Accurate estimation of aquifer parameters is important for calculating groundwater flow and canal seepage. Seepage computed using computer models is inaccurate if the aquifer parameters are inaccurate, regardless of the accuracy of the algorithms. In South Florida, calibration of regional parameters is not a simple process considering that the physical system itself is complex, and the state variables of the system depend heavily on complicated operational rules. A typical water level or discharge time series record in South Florida shows primarily the effects of rainfall and evapotranspiration (ET) on the surface and sub-surface system, and superimposed over it, the effects of local and regional stresses due to structure and pump operations by utilities and agricultural users, among others. Under these complex conditions, calibrations based on optimization or manual methods may be difficult at times. A key reason for the difficulty is the lack of understanding of the cause and effect relationships between

A fully integrated regional simulation model (RSM) has been developed to simulate the complex hydrologic system of South Florida. The South Florida system consists of a large integrated overland flow system, a groundwater flow system and a canal flow system. Implicit solution methods, efficient sparse solvers, and object oriented methods have made it possible to solve large complex systems simultaneously with practically any time step and cell size, even when the numerical errors can be extremely large. The current study is aimed at understanding the numerical error due to a boundary disturbance under a variety of spatial and temporal discretizations and solution characteristics. The errors are compared with the analytical estimates obtained by Lal (2000) for finite difference problems. Results of the study are useful in determining optimal spatial and temporal discretizations for model applications.

The weighted implicit finite volume approach for 2-D flow is extended to model canal flow in the South Florida Regional Simulation Model (SFRSM). St Venant equations with the diffusion approximation are used as governing equations. The water body and water mover base classes are used to represent canal segments and junctions in the 1-D model in an object oriented framework. Ground water and surface water flow is integrated with canal flow through flow functions attached to segment walls. The model uses an external sparse solver to solve overland, ground and canal flows simultaneously. The method is stable because of the implicit formulation. This paper describes the theory and provides a sample application.