DETERMINISTIC MODELS FOR PREDICTING RESIDENTIAL WATER CONSUMPTION1

ABSTRACT: Forecasts of future urban water demand traditionally have been made by the projection of historic trends in per capita consumption and population. This paper outlines the use of two deterministic models to forecast the residential component of urban water demand. The models incorporate specific representation of the activities which result in water consumption at each residence. Predictions of water use can then be made by modeling the changes expected in the number of these activities and the consumption for each such activity.     

THE POTENTIAL FOR INCREASING STREAMFLOW FROM SIERRA NEVADA WATERSHEDS1

The Sierra Nevada produces over 50 percent of California's water. Improvement of water yields from the Sierra Nevada through watershed management has long been suggested as a means of augmenting the state's water supply. Vegetation and snowpack management can increase runoff from small watersheds by reducing losses due to evapotranspiration, snow interception by canopy, and snow evaporation. Small clearcuts or group selection cuts creating openings less than half a hectare, with the narrow dimension from south to north, appear to be ideal for both increasing and delaying water delivery in the red fir-lodgepole pine and mixed-conifer types of the Sierra west slope. Such openings can have up to 40 percent more snow-water equivalent than does uncut forest. However, the water yield increase drops to 1/2-2 percent of current yield for an entire management unit, due to the small number of openings that can be cut at one time, physical and management constraints, and multiple use/sustained yield guidelines. As a rough forecast, water production from National Forest land in the Sierra Nevada can probably be increased by about 1 percent (0.6 cm) under intensive forest watershed management. Given the state of reservoir storage and water use in California, delaying streamflow is perhaps the greatest contribution watershed management can make to meeting future water demands.     

ORDER CLASSIFICATION OF URBAN CATCHMENTS1

ABSTRACT: Stream order systems provide useful classification methods according to the number of tributaries collected. In urban catchments, sewer line order is a concepot concept providing for the same type of classification. Horton's stream order system is used to classify sewers beginning with the smallest lines as first order to the largest main sewer which is sixth order for two catchments studied. Average tributary area, average length and number of lines are shown as functions of order. The bifurcation ratios are also presented. They can be used for finding the number of sewer lines in the next order. The number of first order lines depend on lot size and the bifurcation ratios vary widely.     

Deposition and removal of fugitive dust in the arid southwestern United States: measurements and model results

This work was motivated by the need to better reconcile emission factors for fugitive dust with the amount of geologic material found on ambient filter samples. The deposition of particulate matter with aerodynamic diameter less than or equal to 10 microm (PM10), generated by travel over an unpaved road, over the first 100 m of transport downwind of the road was examined at Ft. Bliss, near El Paso, TX. The field conditions, typical for warm days in the arid southwestern United States, represented sparsely vegetated terrain under neutral to unstable atmospheric conditions. Emission fluxes of PM10 dust were obtained from towers downwind of the unpaved road at 7, 50, and 100 m. The horizontal flux measurements at the 7 m and 100 m towers indicated that PM10 deposition to the vegetation and ground was too small to measure. The data indicated, with 95% confidence, that the loss of PM10 between the source of emission at the unpaved road, represented by the 7 m tower, and a point 100 m downwind was less than 9.5%. A Gaussian model was used to simulate the plume. Values of the vertical standard deviation sigma(z) and the deposition velocity Vd were similar to the U.S. Environmental Protection Agency (EPA) ISC3 model. For the field conditions, the model predicted that removal of PM10 unpaved road dust by deposition over the distance between the point of emission and 100 m downwind would be less than 5%. However, the model results also indicated that particles larger than 10 microm (aerodynamic diameter) would deposit more appreciably. The model was consistent with changes observed in size distributions between 7 m and 100 m downwind, which were measured with optical particle counters. The Gaussian model predictions were also compared with another study conducted over rough terrain and stable atmospheric conditions. Under such conditions, measured PM10 removal rates over 95 m of downwind transport were reported to be between 86% and 89%, whereas the Gaussian model predicted only a 30% removal. One explanation for the large discrepancy between measurements and model results was the possibility that under the conditions of the study, the dust plume was comparable in vertical extent to the roughness elements, thereby violating one of the model assumptions. Results of the field study reported here and the previous work over rough terrain bound the extent of particle deposition expected to occur under most unpaved road emission scenarios.     

Chemical (polycyclic aromatic hydrocarbon and heavy metal) levels in contaminated stormwater and sediments from a motorway dry detention pond drainage system

Chemical (polycyclic aromatic hydrocarbon - PAH and heavy metal) levels in stormwater and sediment samples collected from the London Orbital (M25) motorway drainage dry detention pond at Oxted, Surrey, UK were determined. Such chemicals are derived from vehicular combustion products and the wear and tear materials deposited onto the motorway surface. Gas chromatography-mass spectrometry (GC-MS) was used for the qualitative and quantitative determination of 16 USEPA priority PAHs in motorway drainage sediments. The GC-MS method, incorporating a solid phase extraction step, provides detection limits ranging from 0.17 to 0.41 mg kg(-1)(dry weight). Almost all of the 16 USEPA listed PAHs were detected. Phenanthrene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(a)pyrene and benzo(g,h,i)perylene (PAH numbers 5, 7, 8, 9, 10, 11, 13 and 16) were among the PAHs found at "higher" levels (ranging from 0.3-10.2 mg kg(-1), dry weight) in the sediment samples. PAH levels show little change along the motorway drainage silt trap (facility for reducing the levels of suspended particulate matter in the stormwater). PAH concentrations are considerably higher in the dry detention pond outflow interceptor. Statistical analysis showed that significant correlation coefficients (based on a t-test at the 95% confidence interval) were obtained between those PAHs found at high concentrations over all of the sampling sites. Several PAHs were dispersed beyond the treatment facility and accumulation in the sediment of the deer park resulted in levels ranging from 0.3-1.6 mg kg(-1), dry weight. These PAHs found beyond the treatment facility (in the local farm deer park) may contribute a serious health threat to farm animals or even fish in the aquatic environment. Heavy metal levels (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, Sb and Pb) of the drainage stormwater and sediments were determined by inductively coupled plasma mass spectrometry (ICP-MS), with quality control evaluation using two certified reference materials. Typical detection limits were found to be below 0.1 [micro sign]g l(-1) for stormwater and 0.005 mg kg(-1) for acid digested sediments. Raised heavy metal levels were found throughout the dry detention pond facility and only decrease when the stormwater is diluted following discharge into the river Eden. Statistical analysis also confirms that some significant correlations exist between various heavy metals and PAHs. However, no overall conclusive trend is found indicating that a particular PAH is deposited in sediment relative to a specific heavy metal/s. These results raise some serious concerns about the dispersion and accumulation of chemicals in the sediments of motorway stormwater drainage systems and the need for maintenance and clean-up of contaminated material from such systems.     

Modelling soil series data to facilitate targeted habitat restoration: a polytomous logistic regression approach

Habitat restoration at a landscape scale is becoming increasingly important in environmental management. In this context, geographical information systems are well suited as they can store and integrate many of the abiotic and biotic criteria used to assess the ecological worth of a site. However, this capacity can be limited by the availability or suitability of spatial data sets. A classic example of the latter case is the National Soil Map of England and Wales, which groups soils of a varied nature into associations. Consequently the national soil map has proved to be a poor predictor of habitat suitability. Using polytomous logistic regression we put forward a method for separating soil associations into their constituent soils within the Chilterns Natural Area. This approach used soil association, aspect, slope and relative height as variables for this analysis. Whilst the model's performance is likely to have been limited by the accuracy of the soil association data set, a predictive accuracy of between 47 and 65% is sufficient to facilitate better targeting of habitat restoration when combined with other abiotic factors such as climate and topography.     

Economic growth,biodiversity loss and conservation effort

This paper investigates the relationship between economic growth, biodiversity loss and efforts to conserve biodiversity using a combination of panel and cross section data. If economic growth is a cause of biodiversity loss through habitat transformation and other means, then we would expect an inverse relationship. But if higher levels of income are associated with increasing real demand for biodiversity conservation, then investment to protect remaining diversity should grow and the rate of biodiversity loss should slow with growth. Initially, economic growth and biodiversity loss are examined within the framework of the environmental Kuznets hypothesis. Biodiversity is represented by predicted species richness, generated for tropical terrestrial biodiversity using a species-area relationship. The environmental Kuznets hypothesis is investigated with reference to comparison of fixed and random effects models to allow the relationship to vary for each country. It is concluded that an environmental Kuznets curve between income and rates of loss of habitat and species does not exist in this case. The role of conservation effort in addressing environmental problems is examined through state protection of land and the regulation of trade in endangered species, two important means of biodiversity conservation. This analysis shows that the extent of government environmental policy increases with economic development. We argue that, although the data are problematic, the implications of these models is that conservation effort can only ever result in a partial deceleration of biodiversity decline partly because protected areas serve multiple functions and are not necessarily designated to protect biodiversity. Nevertheless institutional and policy response components of the income biodiversity relationship are important but are not well captured through cross-country regression analysis.     

An examination of the compatibility of World Bank policies towards population, development and biodiversity in the Third World

This paper addresses the compatibility of World Bank policies towards population growth, development and biodiversity in the Third World. The World Bank has been central to the design and implementation of the Global Environment Facility (GEF), the remit of which includes the conservation of global biodiversity. However, the Bank's influence over the facility has in itself created controversy which may undermine its effectiveness. More significantly, the Bank's commitment to the GEF is subverted by its policies in other social and economic sectors. The World Bank, together with the International Monetary Fund (IMF), directs the structural adjustment of Third World economies through economic deregulation and privatization. This approach exacerbates inequalities and further empowers large landowners who may then displace tenant farmers and claim exclusive rights to former common land. Thus, biodiversity loss occurs as large landowners reorientate the land use towards the production of export goods and dispossessed farmers invade marginal land. Population growth influences biodiversity loss through its contribution to agricultural intensification and the settlement of marginal land. The World Bank encourages this trend through its non-committal approach to population control, but more especially through structural adjustment's positive effect on fertility.     

FLOW DURATION CURVES II: A REVIEW OF APPLICATIONS IN WATER RESOURCES PLANNING1

ABSTRACT: A streamflow duration curve illustrates the relationship between the frequency and magnitude of streamflow. Flow duration curves have a long history in the field of water-resource engineering and have been used to solve problems in water-quality management, hydropower, instream flow methodologies, water-use planning, flood control, and river and reservoir sedimentation, and for scientific comparisons of streamflow characteristics across watersheds. This paper reviews traditional applications and provides extensions to some new applications, including water allocation, wasteload allocation, river and wetland inundation mapping, and the economic selection of a water-resource project.