Journal of Water Resources Planning and Management

A mathematical model is developed to estimate trihalomethane formation potential (THMFP) in Lake Youngs, Wash. The model simulates both seasonal trends and spatial variations. The model kinetic framework includes total organic carbon (TOC), THMFP, chlorophyll a, zooplankton, Secchi disk depth, dissolved oxygen, dissolved TDP, and total phosphorus (TP). Calculated THMFP concentrations are dependent on external watershed TOC loading, algal cell densities, and TOC associated with extracellular products. Model performance is evaluated by comparison of calculated results with measured data from Lake Youngs. Analyses illustrate how THMFP concentrations in the raw water supply change as a function of watershed TP and TOC loading. A general assessment considers the role of watershed land-use control, reservoir management, alternative treatment technologies, and the operation of the water supply distribution system in complying with finished drinking water standards for THM.

An integrated decision support system (DSS) that aids the operation of a tank (small-scale reservoir) irrigation system in south India is described. The DSS includes data subsystem, a model subsystem, a knowledge base, and a user interface. The knowledge base of the DSS was developed from the knowledge derived from field experts as well as from the results of an optimization model. The DSS was evaluated to assess its decision-making capability using five years of data. Shortages in irrigation water supply simulated from the DSS were less than those occurring in the actual operation practiced by water authorities. The forecasts of system variables, namely, inflow and evapotranspiration were found to be adequate for real-time operation of the tank system.

Control methods are applied to sewer network flow in the aim of reducing pollution of receiving waters. A multilayer control structure consisting of an adaptation, an optimization, and a direct control layer may be used for the solution of the complex control problem. Several approaches have been proposed with regard to the optimization layer. This paper focuses on the comparison of two methods, the nonlinear optimal control and the multivariable feedback control. For the numerical solution of the nonlinear optimal control problem a feasible direction algorithm is used, and for the design of the linear multivariable feedback regulator a linear-quadratic approach is applied. A detailed study of the central control problem for a particular sewer network is presented using these two methods and comparing their respective efficiency. Results indicate a slight superiority in terms of efficiency of the nonlinear optimal control approach for the price of an increased, but real-time, feasible computational effort.

A method to determine water losses from distribution networks, domestic connections, unauthorized connections, and domestic meters is presented. This method is based on stratified random sampling and leak flow gauging at connections, observation of users with low monthly consumptions, verification of house flow meters, and measurements in hydrometric districts. The results allow for the identification and causation of water losses in different areas of a city and for planning the actions that must be programmed to prevent additional losses. The method was applied to the drinking water distribution networks in 15 Mexican cities. Of the water supplied to urban distribution systems 24.5 is lost from house connection leaks, 10.6 from defects in mains and secondary lines, and 1.3 due to meter underregistry.

Erosion of riverbank property is a frequent occurrence along the dynamic river systems within Snohomish County. In the mid-1980s the County established a legal mechanism that allowed the county to cost-share bank stabilization projects with private landowners, where the project could also be demonstrated to have a public benefit. To date, the program has completed over 250 bank stabilization projects. Projects have evolved from historic bank stabilization techniques that relied largely on end dumping of large rock along eroded riverbanks to more technical and cost-effective methods that strive to work with the forces of a river as well as protect against those forces. These methods, often called bioengineering, combine engineering materials such as rock and geotextile matting with live native plants. Incorporating live native plants within these structures benefits riparian wildlife and improves salmon habitat. Recent flood-hazard–management planning efforts have produced additional recommendations to enhance the program.

Amount, heavy metal content, organic content, and mass distribution of the bottom sediment in an 18 year old, single-purpose dry storm water detention basin were measured. The measured results were used to assess the effect of sedimentation on flood control capacity and the applicability of recommended values for predicting amounts of sediment and heavy metal accumulation. The rate of sediment accumulation was measured to be 0.8 cm per year. Because of sedimentation, the flood control capacity of the basin was estimated to have decreased from that for the 13-year storm to that for the 4-year storm. Both the soil erosion rate and the suspended solid concentration recommended for predicting the amount of sediment accumulation appear to be applicable for this basin. However, recommended metal trap efficiencies, recommended concentrations of heavy metals in runoff, or both appear to be too high for predicting the amount of heavy metal accumulation in this basin.

A water quality modeling project was undertaken to estimate non-point-source loading and associated water quality impacts for the Carson River in Nevada. As part of the modeling initiative, the WASP5 program was modified to simulate attached algae. Simulation results showed that a 48 reduction of total phosphorus (TP) load would be required to achieve the existing in-stream TP annual average standard of 0.10 mg-P/L. While this reduction decreased the predicted areal extent of water quality degradation, stream reaches immediately downstream of agricultural loading still experienced high algal populations and large concomitant diel dissolved oxygen fluctuations due to the fact that phosphorus is not rate limiting for algae growth at concentrations near 0.10 mg-P/L. A simulated 97 reduction of TP load was required to decrease significantly the population of attached algae, while only a 70 reduction of total non-point-source loading (both nitrogen and phosphorus) achieved similar results.