Analysis of bank erosion on the Merced River,Yosemite Valley,Yosemite National Park,California, USA

Channel changes from 1919 to 1989 were documented in two study reaches of the Merced River in Yosemite National Park through a review of historical photographs and documents and a comparison of survey data. Bank erosion was prevalent and channel width increased an average of 27% in the upstream reach, where human use was concentrated. Here, trampling of the banks and riparian vegetation was common, and banks eroded on straight stretches as frequently as on meander bends. Six bridges in the upper reach constrict the channel by an average of 38% of the original width, causing severe erosion. In the downstream control reach, where human use was minimal, channel widths both decreased and increased, with a mean increase of only 4% since 1919. Bank erosion in the control reach occurred primarily on meander bends. The control reach also had denser stands of riparian vegetation and a higher frequency of large woody debris in channels. There is only one bridge in the lower reach, located at the downstream end. Since 1919, bank erosion in the impacted upstream reach contributed a significant amount of sediment (74,800 tonnes, equivalent to 2.0 t/km²/yr) to the river. An analysis of 75 years of precipitation and hydrologic records showed no trends responsible for bank erosion in the upper reach. Sediment input to the upper reach has not changed significantly during the study period. Floodplain soils are sandy, with low cohesion and are easily detached by lateral erosion. The degree of channel widening was positively correlated with the percentage of bare ground on the streambanks and low bank stability ratings. Low bank stability ratings were, in turn, strongly associated with high human use areas. Channel widening and bank erosion in the upper reach were due primarily to destruction of riparian vegetation by human trampling and the effect of bridge constrictions on high flow, and secondarily to poorly installed channel revetments. Several specific recommendations for river restoration were provided to park management.     

Wellhead treatment costs for groundwater contaminated with pesticides: A preliminary analysis for pineapple in Hawaii

In Hawaii, trace concentrations of pesticides used in the production of pineapple were found in the groundwater supplies of Mililani Town in the Pearl Harbor Basin on the island of Oahu. Groundwater serves as the major source of drinking water and residents pay for wellhead treatment of the contaminated water, via their monthly water bill. The agricultural chemical users within the Pearl Harbor Basin do not include these wellhead treatment costs in their production costs. The agricultural industry benefits from using pesticides but does not pay the entire societal cost of using these chemicals. In this study we evaluate the specific financial cost of wellhead treatment, and not the economic value of groundwater. While wellhead treatment costs could conceivably be shared by several parties, this study focuses on the financial impact of the pineapple industry alone. This study factors annual wellhead treatment costs into annual pineapple production costs to measure the effect on annual financial return from pineapple production. Wellhead treatment costs are calculated from the existing granulated activated carbon (GAC) water treatment facility for Millilani Wells I and II. Pineapple production costs are estimated from previous cost of production studies. The inclusion of wellhead treatment costs produces different production-cost results, depending on the scale of analysis. At the local scale, the Mililani wellhead treatment costs can be factored into the production costs of the pineapple fields, which were probably responsible for contamination of the Mililani Wells, without causing a deficit in economic return. At the larger regional scale, however, the return from all of the pineapple grown in the Pearl Harbor Basin can not sustain the cost of wellhead treatmentfor the entire water supply of the basin. Recommendations point to the prevention of groundwater contamination as more cost-effective measure than wellhead treatment.     

Evaluation of tidal marsh restoration: Comparison of selected macroinvertebrate populations on a restored impounded valley marsh and an unimpounded valley marsh within the same salt marsh system in Connecticut,USA

Macroinvertebrates were examined on an impounded valley marsh in Stonington, Connecticut, that has changed from aTypha-dominated system to one with typical salt-marsh vegetation during 13 years following the reintroduction of tidal exchange. Animal populations on this restored impounded marsh were evaluated by comparing them with populations on a nearby unimpounded valley marsh of roughly the same size. Populations of the high marsh snail,Melampus bidentatus Say, were quantitatively sampled along transects that extended from the water-marsh edge to the upland; those of the ribbed mussel,Geukensia demissa Dillwyn, were sampled in low marsh areas on transects along the banks of creeks and mosquito ditches. The occurrence of other marsh invertebrates also was documented, but their abundance was not measured. The mean density ofMelampus was 332±39.6 SE/m² on the restored impounded marsh and 712±56.0 SE/m² on the unimpounded marsh. However, since snails were larger on the restored impounded marsh, the difference in snail biomass was less pronounced than the difference in snail density. MeanMelampus biomass was 4.96±0.52 SE g dry wt/m² on the restored impounded marsh and 6.96±0.52 SE g dry wt/m² on the unimpounded marsh. On the two marshes, snail density and biomass varied in relation to plant cover and other factors. The density and biomass ofGeukensia at the edge of the marsh were comparable on the restored impounded and unimpounded marshes. Mean mussel densities ranged from 80 to 240/m² and mean mussel biomass varied from 24.8–64.8 g dry wt/m² in different low marsh areas. In contrast, below the impoundment dike, meanGeukensia density was 1100±96.4 SE/m² and meanGeukensia biomass was 303.6±33.28 SE g dry wt/m². A consideration of all available evidence leads to the conclusion that the impounded marsh is in an advanced phase of restoration.     

General mathematical models for LCI recycling

Life cycle inventory (LCI) is becoming more widely used as a tool to evaluate the resource and energy use and the environmental releases associated with various products. The methodology for handling different recycling scenarios is also becoming increasingly important. Several different methods exist for handling recycling in an LCI. The method described in this paper uses mathematical models to show that the same basic equations can be used to handle a variety of recycling options for multi-product systems.     

The costs to farmers and estate owners of public access to the countryside

This paper considers the external costs of public access on privately‐owned farm and estate land in Scotland. The increased costs and reductions in income associated with public access are found to be highly variable and site‐specific, with the main effects on land in areas of high population density or high scenic quality, or with recreational attributes. Although costs were on average higher for estates, reflecting their larger area and recreational potential, on a per‐hectare basis the costs of access were greater for the farm sector. Whilst much of the public access exists through de facto rights on open‐access land, there was evidence for an increasing commercialization of open‐air recreation, particularly with respect to more specialized activities. The discussion considers the extent to which the costs of access for land managers are reflected in policies determining the public provision of countryside access.     

Development of a Computer Workstation for Famine Early Warning and Food Security

Beginning in 1990, the University of Arizona, Arizona Remote Sensing Center (ARSC) has been involved in a collaborative effort with the Global Information and Early Warning System (GIEWS) and the Remote Sensing Center of the Food and Agriculture Organization (FAO) of the United Nations in designing and developing an integrated computer workstation for famine early warning. The goal of the project is to provide food security analysts with a set of computer tools to manage a very large and diverse set of data for predicting the onset of food security emergencies for every country on Earth. The initial stage of the project involved the conceptual definition of system elements and the development of overall system architecture. We are now developing an open, flexible, and portable system designed to significantly assist the work of the analysts. System architecture provides a task-specific and user-friendly graphic user interface (GUI) within a Windows environment that will link image processing, geographic information system (GIS), spreadsheet, text, and graphics software packages into a single operational environment. A relational database management system (RDBMS) is serving as the back-end of the workstation to facilitate data storage and retrieval and as a means to preserve analysis methodologies.     

COMPUTATION OF UNSTEADY FLOWS IN THE ALABAMA RIVER1

ABSTRACT: An application is described of the branch-network flow model, BRANCH, to the upper Alabama River system in central Alabama. The model is used to simulate one-dimensional unsteady flows and water surface elevations in approximately 60 river miles of the Alabama River system. Preliminary calibration was made using 72 hours of observed data. Simulated discharges are about 10 percent lower than observed discharges at higher discharge rates and computed flows lag observed flows by about 30 minutes.     

COMPARISON OF RESERVOIR LINEAR OPERATION RULES USING LINEAR AND DYNAMIC PROGRAMMING1

ABSTRACT: Mathematical optimization techniques are used to study the operation and design of a single, multi-purpose reservoir system. Optimal monthly release policies are derived for Hoover Reservoir, located in Central Ohio, using chance-constrained linear programming and dynamic programming-regression methodologies. Important characteristics of the former approach are derived, discussed, and graphically illustrated using Hoover Reservoir as a case example. Simulation procedures are used to examine and compare the overall performance of the optimal monthly reservoir release policies derived under the two approaches. Results indicate that, for the mean detention time and the corresponding safe yield target water supply release under existing design of Hoover Reservoir, the dynamic programming policies produce lower average annual losses (as defined by a two-sided quadratic loss function) while achieving at least as high reliability levels when compared to policies derived under the chance-constrained linear programming method. In making this comparison, the reservoir release policies, although not identical, are assumed to be linear. This restricted form of the release policy is necessary to make the chance-constrained programming method mathematically tractable.