ABSTRACT: The effects of potential climate change on water resources in the Delaware River basin were determined. The study focused on two important water‐resource components in the basin: (1) storage in the reservoirs that supply New York City, and (2) the position of the salt front in the Delaware River estuary. Current reservoir operating procedures provide for releases from the New York City reservoirs to maintain the position of the salt front in the estuary downstream from freshwater intakes and ground‐water recharge zones in the Philadelphia metropolitan area.A hydrologic model of the basin was developed to simulate changes in New York City reservoir storage and the position of the salt front in the Delaware River estuary given changes in temperature and precipitation. Results of simulations indicated that storage depletion in the New York City reservoirs is a more likely effect of changes in temperature and precipitation than is the upstream movement of the salt front in the Delaware River estuary. In contrast, the results indicated that a rise in sea level would have a greater effect on movement of the salt front than on storage in the New York City reservoirs. The model simulations also projected that, by decreasing current mandated reservoir releases, a balance can be reached wherein the negative effects of climate change on storage in the New York City reservoirs and the position of the salt front in the Delaware River estuary are minimized. Finally, the results indicated that natural variability in climate is of such magnitude that its effects on water resources could overwhelm the effects of long‐term trends in precipitation and temperature.

This report describes a method, based on random subsampling of real data, for comparison of network-design technologies that have a common objective.Two such technologies, Network Analysis for Regional Information (NARI) and Network Analysis Using Generalized Least Squares (NAUGLS), were chosen to illustrate the comparison technique by using a data base from a network of gages in the central part of the United States.In general, the results for the illustrative example indicate that the NAUGLS method conveys more information than the NARI method to the network designer interested in maximizing regional information about mean annual flows given a limited budget.

A summary of the results of a cost-effectiveness study of the U.S. Geological Survey stream-gauging program in 17 states is contained in this paper. The results are for the first year of a five year nationwide study undertaken by the U.S. Geological Survey. The objective of the study is to define and document the most cost-effective means of furnishing streamflow information. The first step of this study involved identification of data uses and funding sources for 1,939 continuous-record stations currently being operated with a budget of $11,425,650. Only 35 continuous-record stations were identified as not having sufficient justification to continue their operation. In addition, 31 more short-term special study stations were identified as not having justified data uses beyond completion of their respective studies. In the second step, evaluation of alternative methods of providing streamflow information, flow-routing and regression models were developed for estimating daily flows at 145 stations of the 1,939 stations analyzed. Only six of the 145 stations that were analyzed were considered to have acceptable accuracy of the simulated flows for the intended uses of the data. Based on the accuracy of the simulated flows, the operation of continuous-record gauging stations at these locations could be discontinued. In the third step of the analysis, relationships were developed between the accuracy of the streamflow records and the oerating budget. For the current operating budget, the weighted average standard error was 21.0 percent for the programs analyzed in the 17 states. By redistribution of resources among the stations according to an optimization program, this weighted average standard error can be reduced to 19.0 percent. The current weighted average standard error of 21.0 percent can conversely be achieved with a reduced budget of $10,889,800, a total budget reduction of $535,850.

Data uses and funding sources were identified for the 51 continuous stream gages currently being operated in Maine. Three stream-gages were identified as having insufficient reason to continue their operation. Operation of these stations were identified as having uses specific only to short-term studies; it is recommended that these stations be discontinued at the end of the data-collection phases of the studies. The remaining 45 stations should be maintained in the program for the foreseeable future. The current policy for operation of the 45-station program would require $180,300 per year. The average standard error of estimation of streamflow record is 18.5 percent. It was shown that this overall level of accuracy at the 45 sites could be maintained with a budget of \$170,000 if the gaging resources were redistributed among the gages. A minimum budget of \$155,000 is required to operate the 45-gage program; a budget less than this does not permit proper service and maintenance of the gages and recorders. At the minimum budget, the average standard error is 26.0 percent. The maximum budget analyzed was \$350,000, which resulted in an average standard error of 9.2 percent. Large parts of Maine 's interior were identified as having sparse stream-flow data. It was recommended that this sparsity should be remedied as funds can be made available. (USGS)

As an aid to the administration of the Colorado River Compact of 1922, certain streaingaging stations were established by the U.S. Geological Survey where the flow of the main river, its tributaries and subsequent diversions, and return flows were to be measured.The U.S. Supreme Court ruling (Arizona versus California, 1963) on the relative rights of two of the Lower Basin States-California and Arizona-led to a major increase in streamgaging activity by the Geological Survey in the Lower Basin.The effectiveness of the resulting data in the administration of the Compact and implementation of the court ruling is analyzed.The streamgaging operations of 60 stations currently operated in the Lower Colorado River Basin are assessed from a cost-effective viewpoint using the sum of the uncertainties associated with estimating the annual mean discharge at each station as an inverse surrogate for the economic worth of data.The current service center for each station-either Blythe, California, or Yuma, Arizona-was-not changed but the available funds were shifted from the operation of one station to another and, in some cases, from one office to the other, as efficiency dictated.The analysis shows that the current budget can be expended in such a way as to reduce the current level of uncertainty by 54 percent.Alternatively, the current level of uncertainty can be attained with a reduction of 53 percent in the current annual budget of $296,500.

The concept of equivalent years of record, a measure of parameter accuracy, in conjunction with regression analysis simulation leads to a methodology for specifying sets of numbers of gauging sta­ tions and lengths of record required to attain a prespecified level of regional streamflow-parameter accu­ racy. This methodology can be used in network design to identify the number of stations and length of record that is the least cost network that meets the accuracy criteria. The methodology also indicates situations in which the criteria cannot be met without improving the underlying regionalization model. La conception des réseaux pour les données des eaux de surface qui fourniront des renseignements régionaux Résumé. Le concept d'années enregistrées équivalentes, servant à mesurer l'exactitude des paramètres, en relation avec un simulacre d'analyse par régression, mène à une méthodologie permettant de spécifier les ensembles de nombres de stations fluviometriques et d'années enregistrées requis pour parvenir à un degré prédéterminé de précision dans les paramètres régionaux de débit. Cette méthodologie peut être^ utilisée, lors de la conception des réseaux, afin d'identifier le nombre de stations et d'années enregistrées représentent le réseau au moindre coût répondant au critère d'exactitude. La méthodologie indique éga­ lement les situations où le critère ne peut être satisfait sans améliorer le modèle de régionalisation de base.

This report describes the theoretical developments and illustrates the applications of techniques that recently have been assembled to analyze the cost-effectiveness of federally funded stream-gaging activities in support of the Colorado River compact and subsequent adjudications. The cost effectiveness of 19 stream gages in terms of minimizing the sum of the variances of the errors of estimation of annual mean discharge is explored by means of a sequential-search optimization scheme. The search is conducted over a set of decision variables that describes the number of times that each gaging route is traveled in a year. A gage route is defined as the most expeditious circuit that is made from a field office to visit one or more stream gages and return to the office. The error variance is defined as a function of the frequency of visits to a gage by using optimal estimation theory. Currently a minimum of 12 visits per year is made to any gage. By changing to a six-visit minimum, the same total error variance can be attained for the 19 stations with a budget of 10% less than the current one. Other strategies are also explored. (USGS)

Procedures that traditionally have been used to size water-supply reservoirs and to design related treatment plants and distribution systems have ignored the powerful tool of economic marginal analysis. Marginal analysis, when combined with Bayesian techniques, can be used to specify optimum designs for water supplies that are dominated by the need for over-year storage of streamflow. The combination of these two tools also provides a means for evaluating the alternative of collecting additional streamflow data prior to designing the water-supply system. A simplified example of the Bayesian marginal analysis that has ten years of streamflow data as an input demonstrates the design technique and evaluation of an added year of streamflow data. The economic demand curve and the cost analyses that are contained in the technique are assumed to be known. This assumption limits the utility of the technique until it can be extended to include the economic uncertainties.

The concept of equivalent years of record, a measure of parameter accuracy, in conjunction with regression analysis simulation leads to a methodology for specifying sets of numbers of gauging stations and lengths of record required to attain a prespecified level of regional streamflow-parameter accuracy. This methodology can be used in network design to identify the number of stations and length of record that is the least cost network that meets the accuracy criteria. The methodology also indicates situations in which the criteria cannot be met without improving the underlying regionalization model.

Reviews of current methodologies for the determination of the worth of hydrologic data indicate that each method has certain shortcomings. The simulation approach requires information concerning the statistical properties of the data that are not usually known. The Bayesian Approach often leads to mathematically intractable relations. The two approaches may be combined by defiing the data worth through simulation under the condition of assumed statistical properties and releasing the conditioning by making use of the prior distributions of the unknown statistics obtained from the Bayesian approach. This combined approach circumvents the problems encountered when either the Bayesian or the simulation approach is used exclusively. An example illustrates the use of the combined approach in evaluation of the worth of flood data in the design of highway crossings.

This report describes a technique, Network Analysis of Regional Information (NARI), and the existing computer procedures that have been developed for the specification of the regional information-cost relation for several statistical parameters of streamflow. The measure of information used is the true standard error of estimate of a regional logarithmic regression. The cost is a function of the number of stations at which hydrologic data are collected and the number of years for which the data are collected. The technique can be used to obtain either (1) a minimum cost network that will attain a prespecified accuracy and reliability or (2) a network that maximizes information given a set of budgetary and time constraints.

This paper summarizes the results from the first 3 years of a 5-year cost-effectiveness study of the U.S. Geological Survey (USGS) stream-gaging network. The objective of the study is to define and document the most cost-effective means of furnishing streamflow information. In the first step of this study, data uses were identified for 3,493 continuous-record stations currently being operated in 33 States. In the second step, evaluation of alternative methods of providing streamflow information, flow-routing models and regression models, were developed for estimating daily flows at 251 of the 3,493 stations analyzed. In the third step of the analysis, relation­ ships were developed between the accuracy of the stream- flow records and the operating budget.

ABSTRACT This,paper,summarizes,the,results,from,the first,3 years of a 5-year cost-effectiveness study,of the U.S. Geological,Survey,(USGS) stream-gaging,network.,The objective,of the,study,is to,define,and,document,the,most cost-effective,means,of furnishing,streamflow,information. In the first step of this study, data uses were identified for 3,493 continuous-record stations currently being operated in 33 States. In the second step, evaluation of alternative methods of providing streamflow information, flow-routing models and regression models, were developed for estimating daily flows at 251 of the 3,493 stations analyzed. In the third step of the analysis, relation­ ships,were,developed,between,the,accuracy,of the,stream- flow,records,and,the,operating,budget.