Gerald T. Orlob

San Joaquin salt balance: future prospects and possible solutions.

The San Joaquin River Basin in California is presently in a state of salt imbalance with salt loads derived by natural inflow, importations, and accretions within the basin exceeding the loads carried from the basin by hydrologic outflow and extrabasin transfers. Trends in the rates of accretion and excretion parallel the development of the basin’s water resources for agricultural use. Accompanying this development there has been a progressive depletion of the natural outflow of the San Joaquin River, a principal tributary of the Sacramento-San Joaquin Delta estuarine system, and degradation of the quality of water available to users dependent upon the main stem of the river as a primary source of supply. In the lower river, this degradation has been mitigated in recent years by releases of high quality water impounded by New Melones Dam on the Stanislaus River. Supplies for water quality control from this source are limited and may not be sufficient to meet quality and flow targets in the future in the face of competing demands and continuing degradation of quality in the San Joaquin River. This chapter traces the historical development of salt loading in the basin from 1930 to 1989 by means of a basinwide salt balance accounting of principal accretions and excretions. Alternative scenarios of water quality control, and including reallocation of yield from east side reservoirs, seasonal storage of saline drainage in ground-water systems, and control of imported salt loads, are explored.

Comparison of single mechanism and multi mechanism‐based approaches for kinetics of sediment removal

Abstract The process of cohesive particle sedimentation in aquatic environments is perceived as one of continuous formation of aggregates by coagulation and their separation from the water column by accumulation on the deposition bed. Over the temporal scales of practical interest for natural systems, many physical, chemical, and environmental factors govern the rate of sedimentation, hence a purely physics‐based description has not yet been developed. A new information‐based model that uses experimental information to derive governing parameters, while predicting removal through power law relationships, is proposed and tested. Analytical solutions derived for this model are shown to be applicable over large ranges of concentrations and to various fluid‐sediment environments. Comparisons with numerically derived and observed data show that the analytical model is a versatile tool that improves fundamental understanding of the physical processes involved in sedimentation. The inverse problem of identificat...

The use of Monte Carlo methods in natural resource management models

The Monte Carlo method provides a means of introducing natural variability in data, uncertainty of parameter estimation, chance occurrences and model reliability, into the process of simulation modeling for resource management. The technique is described and demonstrated for a hypothetical application of a Gaussian Plume Dispersion Model to a case of atmospheric pollution. It is concluded that the utility of the Monte Carlo approach lies mainly in providing decision makers with information on the likelihood of extreme occurrences and the inherent reliability of simulation modeling.

Temperature Prediction in the Lower Feather River

This paper summarizes the application of one-dimensional finite element hydrodynamic and water quality models to the lower Feather River in Northern California. The study was precipitated by a perceived need for cold water temperature in river reaches below Oroville Dam where salmon spawning occurs. Releases from Oroville Reservoir and Thermalito Afterbay were shown to have a dramatic effect on water temperatures in those sections of the river. The exact degree to which releases affect river temperature had not been determined prior to this study. Calibration and validation of the models were performed using field measurements of flow, meteorological conditions, and water temperatures obtained during August 1993, August 1994, and September 1994.

Assessing Aquatic Ecosystem Response to Stress

Developing management strategies for sustainable riverine ecosystems, including finding practical solutions for endangered aquatic species preservation, requires an improved understanding of riverine ecosystem behavior under stress. This research seeks to provide a methodology to quantify temporal and spatial changes in ecosystem health induced by environmental stresses. A mechanistic ecosystem response model will be utilized to quantify impacts of natural and anthropogenic stresses, singly or in combination, on sensitive aquatic species. This ecosystem response model is being created by incorporating an ecological routine into an existing hydrodynamic and water quality modeling framework. Initial application of the ecosystem response model investigates impacts of flow regime, water temperature, and salinity on survival, growth, and migration of juvenile chinook salmon in the Sacramento River-San Francisco Bay-Delta system. Progress is reported on development and application of this methodology for determining relationships between stress changes and aquatic ecosystem responses.

Comparison of one- and two-dimensional models for simulation of hydrodynamics and water quality in shallow bays

Abstract A two‐dimensional (2‐D) vertically‐averaged finite element model suite was adapted to investigate the hydrodynamics, water quality (WQ), and sediment‐toxicant transport in San Diego Bay. The hydrodynamic model was calibrated and verified with two sets of observed data. Model predictions were also compared with the results from a previous study wherein a one‐dimensional (1‐D) finite difference approach was used. The 2‐D model predictions of water surface elevations and velocities at specified locations in the bay were generally superior. The results of simulation of WQ constituents (temperature, nitrate‐nitrogen, algae, and dissolved oxygen) using the 2‐D WQ model compared well with the results from the 1‐D WQ model, both in the general trend as well as the specific distribution of constituent concentrations. Investigations were also carried out to determine the spatial and temporal distribution of sediments and a hypothetical sediment‐borne toxicant in the bay. Results were found to be in general...