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<br />001507 <br /> <br />STOCK POND HYDROLOGY <br /> <br />....-.),,',:' <br /> <br /> <br />I <br />t~~~;~.t~~;;: <br />'::~;;'n~; <br /> <br />Methods of Estimating Water Supply <br /> <br />Pre.<;licting the adequacy and reliability of supply for sto,ck ponds <br />is even more complex than for major reservoirs, yet the smallness of a <br />single project discourages extensive fact gathering and analysis. Esti- <br />mating the supply is complicated by the fact that very oft,en the pond is <br />filled from flashy surface runoff and from wet weather springs rather <br />from steady ground-water sources (ASCE, 1949); the watershed area is <br />small so its peculiarities make extrapolation from other areas inexact, <br />and precipitation and runoff information is rarely available for the supply- <br />ing area. In the face of these difficulties, 'the engineer must still make <br />estimates of the supply of water before proceeding with his design of the <br />stock pond. <br /> <br />.ii~:;:.;~k~ <br />\:f;~,\'~: <br />\:-;::~~:.~::-.' <br />:;~~;;~:\ <br />:.~r;~..~~?~:~; <br /> <br /> <br />What information is needed about the water supply? Basically <br />information is needed on the amount, time, distribution, probable rates, <br />and quality of the runoff from a contributing area. The average amount <br />of runoff, itself, is of little value--livestock can't drink averages. An <br />analys is of the hydrograph and an understanding of the short-term distri- <br />but ion of runoff, preferably on a storm basis, with alloJWanc e for snowmelt, <br />are ,:,eeded, and the annual variation in the probable s~pply must be known <br />by the engineer in designing a stock pond, With these" using mass curve <br />or res idual mass tabulation, the engineer can compute the storage needed <br />to meet the demands of the livestock. Such storage is designed to provide <br />carryover water from one period of runoff to the next; however, if such <br />carryover is long, the losses by evaporation and seepage may make carry <br />over impractical. Therefore, periods of minimal ,runoff, generallyassoc" <br />iated with drought conditions will need especially accurate appraisal in <br />estimating the supply of water available to a proposed stock pond. Prob- <br />ability of high runoff rates also,must be assessed for safe design of <br />spillways. <br /> <br />W"lt:.t!'''>~ <br /> <br />Two approaches to estimation of the water supply may be consi- <br />dered: (1)' use of precipitation measurements and precipitation runoff <br />relations, and (2) direct runoff estimation. These two methods will be <br />discussed in some detail. <br /> <br />Use of Precipitation and Precipitation RunoffR'elations <br /> <br />Using precipitation and precipitation runoff relations in estimating <br />water supply has had variable success. The success has been greatest <br /> <br />16 <br />