Climate, Climatic Change, and Water Supply (1977) / Chapter Skim
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Overview and Recommendations
Overview and Recommendations
Pages 1-22
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From page 1... ...
The papers consider only the simpler problems of water shortages, which may or may not be severe enough to be ciassifiecI as droughts and which may or may not have resulted from climatic change, as well as make an assessment of the probable effects of climatic variability and climatic change on the nation's water supply needs, policy, and design. Lack of water hampers population and economic growth in some areas of the world, but even in such areas it is common to think of water as a resource that is renewable within the bounds imposed by a stationary regional climate.
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5. The conflicts resulting from future water shortages, whether from natural climatic variability or climatic change, couIcl be alleviated by adjusting water law along the lines suggested in the 1973 National Water Commission report, Water Policies for the Future.
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8. Future water shortages may be exacerbated by climatic change, but unfortunately the climatologist's current forecast ability is insufficient to air!
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Hydrologists have always realized that Of was itself a random variable, but it was not until the Harvard Water Program of the early 1950's that the importance of this concept was formalized. The Harvard Water Program used very Tong hydrologic sequences dividect into many sequences of length equal to the proposed design life of the water-resource systems to arrive at designs that performed "better" with a variety of sequences and hence for a variety of Ci's.
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From page 5... ...
The Harvard Water Program and its predecessors implicitly assumed constant climate and searched among alternative system designs for the "best" clesign, where best (resign was specified as that which maximizes the net benefits or minimizes the economic regrets. In this volume, Matalas and Fiering discuss the calculus of economic regrets in water-resource design in the light of possible procedural changes that could result from considering forecasts of climatic changes.
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was one of anomalously high persistent runofffrom Me upper Colorado River Basin, apparently the greatest and longest in the last 450 years. This wet period was preceded by a long persistent low flow period during 186~1892.
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Nowhere in the United States is the future collision between avaflable supply and projected use more apparent than in the upper Colorado River Basin, the subject of John Dracup's paper in this volume. Two estimates of the adjustecI-to-"virgin"-flow condition (that is, without upstream diversions and Tosses)
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/S. In other words, low flow probabilities for the Colorado River Basin should not be assessed on the assumption that the annual events have been generated by an independent or short memory generating process.
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imminent, this is not the only area of the country where future water shortages are predictable. The paper by Schwarz considers the humid industrial northeast region and finds very low storage capacities for water.
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on the implicit assumption of noncycTic inciepenclence in the data an unlikely assumption for climatic ciata.~3 Further, it is experimentally verifiable that stochastic processes with low-frequency components can yield! sample functions with numerous "significant" spurious cycles.~4 In addition, it is widely known that "significant" cycles are often introcluced into the analysis by moving average manipulations to smooth what are otherwise noisy data.~5 In spite of those defects to cycle analysis, it is still a popular occupation among a portion of the forecasting community and even supports its own specialty journals, which contain discussions of cycle synchronies observed for almost all wavelengths and phenomena.
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From page 11... ...
callecl the "normal," and the base period is intermittently updated to reflect a more recent "normal." It is instructive to consider these forecasts as they might be viewed by water-resource managers. On the Mohonk Trust lancis are two small reservoirs used for water supply and irrigation, and it is conceivable that these reservoirs might be managed using the publishe(1 30-day forecasts for precipitation and temperature.
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Overview and Recommendations ~ ~~;~.~ ~ ~~ ~ ~ ~ ~~ .~ :~ ~ ~ ~~ ~ ~ ~ ~ ~ ~~ ~ ~ ~ ~ ~: : :: ::::: :~ :~:: :::::: rs^~ ::: ::: :: ~ ~ ~ :~::~ :~:: : : ::: :? : DILL ::::: ~ ~~ ~~:~ ~ :: it: :::::; JANUARY limo 12 ~ :~ ~ -- OCTOBER ~ 975 ~ ~ ;.
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here, support the general conclusion that past climatic forecasts have not been useful to the water-resource planning process. It wouicI be an act of faith to assume that current long-range climatic forecasts are likely to be any more useful to water-resource planners than have past forecasts.
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It is evident that there are those with unshakable convictions who believe that the future water-supply shortages prognosticates! by Dracup for the Upper Colorado River Basin can be avoiclect by the generation of extra snow whenever ancl wherever needled (note that integrated over time this wouicI amount to deliberate climatic change)
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CLIMATIC TRANSFER FUNCTIONS Before the forecast values of future changed climates become useful to hydrologists and water-resource planners, the variables of the climatic forecast have to be converted into the variables of water supply and projected water use. Water-resource designers customarily work with seasonal water-supply values, where the number of seasons varies from 2 to 12 per year.
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to the new climatic regimes. In summation, transfer functions to get from a climatic forecast to water-resource design variable, Cf.
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The third new cause of increased economic uncertainty in the estimates of future water supply is the threat of climatic change, real or imaginecl, which can alter what farmers will plant, as well as what economists think they will plant. At present, we do not know whether climatic change will result in more or less water available for storage behind!
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Litigation is still a major method used to allocate water supplies in the east, and this approach to conflict resolution would appear to be unnecessarily costly, slow, and clumsy. Trelease has many practical suggestions for making water law more responsive to human needs and desires, but he also places "prior appropriation," "interstate compacts," "reserved rights," and "environmental water law" in their appropriate context, both historically and with regard to future climatic change.
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From page 19... ...
Schwarz suggests detailed measures that could alleviate some of these threatened water shortages, but it would appear that without major new regional cooperation, and federal commitment, the northeast will soon suffer water shortages. Dracup discusses the Colorado compact that divides the 1924 estimate of long-term flow equally between the Upper and Lower Basin states.
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Relative importance of variables in water resources planning, Water Resources Res.
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TABLE R.1 Rank Correlations between Forecast and Observed Precipitation for the Period 1961-1970 City Jan.
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The observed output data for the two-year verification period were retained by the WMO Secretariat. For each data set, the model owners used the concurrent observed input and output data for the six-year calibration period to calibrate and develop the parameters of their models and employed the additional two years of observed input data in the verification period to produce a simulated discharge (computed output)
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