TRENDS IN FRESHWATER INFLOW TO SAN FRANCISCO BAY FROM TUE SACRAMENTO-SAN JOAQUIN DELTA1

ABSTRACT: Outflow from the Sacramento-San Joaquin river system (Delta outflow) provides about 90 percent of the freshwater flow to San Francisco Bay. Because this river system also supplies most of the water used in California, some believed that annual freshwater flow to the Bay had declined by as much as 50 to 60 percent as water use increased. Consequently, we studied trends in actual Delta outflow and precipitation for the period 1921 to 1986, which is when Delta outflow data are available. We found that there has been no decrease in the annual Delta outflow over this period. In fact, a statistically significant increase in annual Delta outflow of 87 cfa/yr has occurred during the period 1921 to 1986. One reason that Delta outflow has increased is because precipitation has increased faster than water use. Other contributing factors include increased runoff from land use changes, water imports from other areas, and the redistribution of ground water. In addition, statistically significant seasonal trends in Delta outflow were found. Over the period 1921–1986 Delta outflow decreased in April and May and increased from July through November. Changes in other months were not statistically significant. These seasonal changes result primarily from the operation of upstream flood control and water development projects, which store water in the spring and release it in the summer and fall. These seasonal changes are also influenced by a climatic shift that has decreased spring snowmelt runoff and increased late summer through winter precipitation.     

Problems and constraints in Philippine municipal fisheries: The case of San Miguel Bay,Camarines Sur

The Philippine fisheries accounted for 3.7% of the gross national product at current prices. The sector employed about 990,872 persons. Of the divisions comprising the industry, municipal fisheries continued to contribute the largest share of fish production. However, the sector is beset with problems, many of which are best examplified by the case of San Miguel Bay (SMB). This paper presents the problems and constraints confronting SMB, a common property resource. This bay's open access condition has led to various problems, such as declining fishery resources, depressed socioeconomic conditions, illegal fishing, increasing population, and conflict among resource users. A poor marketing system, low level of fishing technology, fishermen's noncompliance and authorities' lax enforcement of rules and regulations, as well as lack of alternative sources of income further characterize the condition in SMB. Establishment of fishing rights, improvement of the marketing system, provision of alternative sources of income, and improvement of fishing technology were some of the solutions suggested. One major constraint, however, is financial, Comanagement complemented with other management tools has been proposed in addressing the problems in SMB.     

MODELING THE ENVIRONMENTAL EFFECTS OF A NAVIGATION CHANNEL IN A TIDAL BAY1

ABSTRACT: A circulation and salinity model was used to predict the effects of wind, fresh water inflow, and the construction of a navigation channel on Vermilion Bay, Louisiana. The model numerically solved continuity and motion equations and provided a time history and spatial distribution of tidal depths, flows, velocities, and salinity in two lateral dimensions. The model predicted that high south winds or high fresh water inflow would reduce average bay salinities, as would the construction of a channel through Vermilion Bay. The results suggested the main reason for this behavior is the presence of two bay outlets to the Gulf of Mexico.     

TIDAL POWER GENERATION UTILIZING ATMOSPHERIC PRESSURE OR AIR RECIRCULATION1

ABSTRACT: This paper presents research conducted on tidal power generation utilizig atmospheric pressure or air recirculation. The proposed methods in this paper differ from conventional methods. That is, they require simple and relatively inexpensive power generating facilities that would convert the potential energy of the tides into kine tic energy of air for driving the air turbines in a power plant. The characteristics of the new methods are as follows: (1) in tidal power generation utilizing the atmospheric pressure, the air pressure exerted on an air turbine can be maintained at 1 atm regardless of the water head; (2) in tidal power generation utilizing the air recirculation, the air pressure exerted on an air turbine can be made twice as high as the available water head; (3) higher tidal energy conversion efficiency can be obtained by flowing larger quantities of water in a shorter time period; (4) the generating turbines can be located at a convenient place remote from the reservoir; and (5) equipment corrosion due to salt is minimized.     

Integrated Modular Modeling of Water and Nutrients From Point and Nonpoint Sources in the Patuxent River Watershed1

Abstract: We present a simple modular landscape simulation model that is based on a watershed modeling framework in which different sets of processes occurring in a watershed can be simulated separately with different models. The model consists of three loosely coupled submodels: a rainfall‐runoff model (TOPMODEL) for runoff generation in a subwatershed, a nutrient model for estimation of nutrients from nonpoint sources in a subwatershed, and a stream network model for integration of point and nonpoint sources in the routing process. The model performance was evaluated using monitoring data in the watershed of the Patuxent River, a tributary to the Chesapeake Bay in Maryland, from July 1997 through August 1999. Despite its simplicity, the landscape model predictions of streamflow, and sediment and nutrient loads were as good as or better than those of the Hydrological Simulation Program‐Fortran model, one of the most widely used comprehensive watershed models. The landscape model was applied to predict discharges of water, sediment, silicate, organic carbon, nitrate, ammonium, organic nitrogen, total nitrogen, organic phosphorus, phosphate, and total phosphorus from the Patuxent watershed to its estuary. The predicted annual water discharge to the estuary was very close to the measured annual total in terms of percent errors for both years of the study period (≤2%). The model predictions for loads of nutrients were also good (20‐30%) or very good (<20%) with exceptions of sediment (40%), phosphate (36%), and organic carbon (53%) for Year 1.     

MODELING STUDIES FOR PLANNING: THE GREEN BAY PROJECT1

ABSTRACT: A major contaminant monitoring and modeling study is underway for Green Bay, Lake Michigan. Monitoring programs in support of contaminant modeling of large waterbodies, such as for Green Bay, are expensive and their extent is often limited by budget limitations, laboratory capacity, and logistic constraints. Therefore, it is imperative that available resources be used in the most efficient manner possible. This use, or allocation of resources, may be aided through the application of readily available models in the planning stages of projects. To aid in the planning effort for the Green Bay project, a workshop was held and studies designed to aid in the allocation of resources for a year-long intensive field study. Physical/chemical and food chain models were applied using historical data to aid in project planning by identifying processes having the greatest impact on the predictive capability of mass balance models. Studies were also conducted to estimate errors in computed tributary loadings and in-Bay concentrations and contaminant mass associated with different sampling strategies. The studies contributed to the overall project design, which was a collaborative effort with many participants involved in budgeting, field data collection, analysis, processing of data, quality assurance, data management and modeling activities.     

Flood control failure: San Lorenzo River,California

The San Lorenzo River on the central California coast was the site of a major US Army Corps of Engineers flood control project in 1959. By excavating the channel below its natural grade and constructing levees, the capacity of the river was increased in order to contain approximately the 100 year flood. Production and transport of large volumes of sediment from the river's urbanizing watershed has filled the flood control project with sand and silt. The natural gradient has been re-established, and flood protection has been reduced to containment of perhaps the 30 year flood. In order for the City of Santa Cruz, which is situated on the flood plain, to be protected from future flooding,it must either initiate an expensive annual dredging program, or replan and rebuild the inadequately designed flood control channel. It has become clear, here and elsewhere, that the problem of flooding cannot simply be resolved by engineering. Large flood control projects provide a false sense of security and commonly produce unexpected channel changes.     

A LOOK AT THE HUDSON RIVER ESTUARY1

This paper provides background information on the effect of tide waves upon the movement of water in the Hudson River estuary. Computations based on records from three continuous stage recorders and current-meter discharge measurements made throughout a tidal cycle show that peak discharge rates in the estuary at Poughkeep-sie may be as great as 500,000 cubic feet per second and that total daily tidal volumes as great as 20 billion cubic feet move in the estuary. Computation of water movement in the estuary requires precise field data and continued efforts are needed to perfect the data-collection system and the computation procedure in order to adequately define water movement in the Hudson estuary.