PREDICTING INSTANTANEOUS PEAK DEMAND IN RURAL DOMESTIC WATER SUPPLY SYSTEMS1

ABSTRACT: Many rural areas of the United States still have no public domestic water systems. Typical land use patterns in these areas may require 1/2 mile or more of pipe per farm connection. Public systems serving these areas are economically feasible only if realistic short-term peak demand standards are available for their design. The lack of reliable data upon which to establish such criteria has resulted in a large variation in criteria among state and federal agencies involved in financing and in approving construction of these systems. During the summer of 1975 three distribution laterals of a rural system in Utah were master metered and instantaneous peak flows were recorded for 4 months. The metered lines served 4, 12, and 22 farm houses each. The frequency distribution of peak flows has been analyzed and compared with that developed during similar research in Mississippi and with the existing design standards of the Farmers Home Administration and the State of Utah.     

RELIABILITY OF THE DESIGN STORM CONCEPT IN EVALUATING RUNOFF PEAK FLOW1

A comparative study was undertaken to evaluate peak runoff flow rates using (1) a continuous series of actual rainfall events and (2) design storms. The ILLUDAS computer model was used to simulate runoff over a catchment within the city of Montreal, Canada. A ten-year period, five-minute increment rainfall data base was used to derive peak flow frequency curves. Two types of design storms were analyzed: one derived from intensity duration frequency curves (Chicago type), the other from averaging actual rainfall patterns (Huff type). Antecedent soil moisture conditions were considered in the analyses. It was found that the probability distribution of runoff peak flow was sensitive to the choice of design storm pattern and to the antecedent soil moisture condition. A symmetrical, Chicago-type design storm with antecedent dry soil moisture produced a flow frequency curve similar to the one obtained from a series of historical rainfall events.     

THE NATIONAL WATER COMMISSION REVISITED1

ABSTRACT: In 1973 the National Water Commission concluded its five-year study of national water policy by issuing a massive report containing over 200 recommendations for improvements in the way the Nation deals with its water resources. The Carter Administration is now engaged in another water policy review which incorporates many of the policies espoused by the National Water Commission. In this paper, presented at the 13th American Water Resources Conference in Tucson in November of 1977, the author describes the work of the National Water Commission and the actions taken on its recommendations.     

SPECULATIVE POLICY MAKING IN THE ENVIRONMENTAL ARENA1

ABSTRACT: The development of policy in the American political system has been characterized by incremental change, creation of support, bargaining, compromise, pluralistic group interplay, development of social support and political support, technical input, review and consideration. Incrementalism, as it is called, allows policy to develop in tandem with technical knowledge, legislative and executive support, political advantage, and presumably greater certainty concerning the impact of a particular choice. Environmental policy development, one scholar has hypothesized, followed this basic pattern until the late 1960's when policy aspirations began to escalate much faster than the knowledge, organizational arrangements and political support upon which policy implementation depends. This “escalation” hypothesis is examined in this paper, with particular attention given to policy development in West Virginia.     

DESIGN CONSIDERATIONS FOR AMBIENT STREAM QUALITY MONITORING1

ABSTRACT: Existing ambient water quality monitoring programs have resulted in data which are often unsuitable for assessment of water quality trends. A primary concern in designing a stream quality monitoring network is the selection of a temporal sampling strategy. It is extremely important that data for trend assessment be collected uniformly in time. Greatly superior trend detection power results for such a strategy as compared to stratified sampling strategies. In general, it is desirable that sampling frequencies be at least monthly but not greater than biweekly; higher sampling frequencies usually result in little additional information. An upper limit on trend detectability exists such that for both five and ten year base periods it is often impossible to detect trends in time series where the ratio of the trend magnitude to time series standard deviation is less than about 0.5. For the same record lengths trends in records with trend to standard deviation ratios greater than about one can usually be detected with very high power when a uniform sampling strategy is followed.     

INTERACTIVE COMPUTER-AIDED HYDRAULIC DESIGN: CULVERTS1

ABSTRACT: Regular use of interactive computer programs in hydraulic design can materially increase the productivity of designers without sacrificing accuracy. This article considers the hydraulic design of culverts by interactive use of a computer program; this approach most profitably combines the speed and accuracy of the computer with the experience of the designer.     

WATER TREATMENT PLANT STAGING POLICY1

Economics of treatment plant staging or capacity expansions is governed by the initial water demand rate, Q₀; the anticipated demand growth rate, G; the discount rate, D; the cost of operation, maintenance, and repair (OMR); the useful plant life, T, as a function of the quality of design, construction, and OMR; the treatment plant load factor, L_f; the salvage value of the plant at the end of the project period; the efficiency of the plant-staging design, eta; and the length of the project period, T_s. Various staging policies are investigated to find an optimal policy. The desirability of adopting a staging policy is governed by the magnitude of percent savings that can be achieved by adopting this policy instead of a no-staging policy. A detailed analysis of the problem shows that the percent savings because of staging increase with an increase in Q, G, D, T, and eta;. A reduction in the plant load factor increases the total costs. Information about the effect of variation in the parameters should help the planner and designer to work out an economical schedule of treatment plant capacity expansions.     

MIXING INDUCED BY AN INTERNAL HYDRAULIC JUMP1

ABSTRACT The efficiency of an inverted internal hydraulic jump as a mixing and dispersion mechanism in an aquatic environment was examined. The flow considered was a two-dimensional buoyant flow from a shallow channel over a sloping bottom into a deep reservoir. It could be seen that a rapidly varied flow associated with violent turbulent mixing occurred near the point of discharge if specific discharge conditions and downstream controls were met. Downstream from the mixing zone the flow was stably stratified. The main object of the study was to find the conditions under which a turbulent mixing zone occurred and the rate of turbulent entrainment. Energy loss and length of the mixing zone were also investigated. The independent variables were the outlet densimetric Froude number, the density differential between outfall water and receiving water, the relative depths of the upper and lower layers in the stratified flow portion, the total depth, and the slope of the transition. Theoretical calculations had to be confined to a step increase in depth, but experiments in a laboratory flume showed that results obtained with slopes of 23° and 90° were quite similar. Both theory and experiments showed, for example, that dilution (entrainment rates) up to 2:1 (2 parts heated water to one part cold water) can be achieved at very little energy expense and with downstream depths approximately 8 times the outlet depth. Theoretically, any amount of dilution can be obtained, but large depths may be required. Experimental results also indicate that the length of the mixing zone was frequently ten times the value of the outlet densimetric Froude number.     

STATE LEGISLATIVE RESPONSE TO THE CENTRAL ARIZONA PROJECT1

This research deals with the manner in which the Arizona Legislature dealt with the issue of the Central Arizona Project. Due to the massive costs and impact, the Central Arizona Project was handled by the Legislature in a nonroutinized manner. There was no Legislative precedent for dealing with such a major public work project. Given the Legislature's annual program concerns and priorities, it is neither structurally nor psychologically geared to respond to the Central Arizona Project in terms of placing it within an agenda of priorities even for discussion.     

LAND USE FUNCTION IN WATER QUALITY MANAGEMENT1

ABSTRACT. The Nation has entered a new era of water quality management in which land use policy and regulation must assume an increasingly important role. The benefits of tertiary and advanced waste treatment may be offset by contradictory land use and pollution from land runoff. Unless land use planning and controls are included in water quality management, land-imposed constraints on water quality can be anticipated. Pollution from major types of land runoff are reviewed with respect to sources, effects, and control procedures. Emphasis is given to land use practices and controls. The crucial issue with regard to the latter is lack of land use policies at federal, state, and local levels. State legislation establishing guidelines and minimum standards for land use regulation by local government is required. The dependency of water quality on land use points to the fallacy of attempting to provide for comprehensive water pollution control outside the context of comprehensive land-water resource planning and management.