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on nonirrigated croplands in the watershed_ A watershed protection project is operational in the Spring Creek Watershed above Pierce. This project promotes the use 0' conservation ti I lage as an erosion prevention measure on nonirrigated croplands. It is expected that most nonin"igated c,"opland will be impacted by either the watershed project or provisions in the 'ood security act. The 'ood security act is expected to cause a conversion 0' about 7000 ac of nonjYYisated cropland to permanent cover and prc/mote conset~vation ti IlagE on the remaining nonirrigated cropland. With this di"erence in the watershed, hydrologic curve numbers wi I I probably be lower than values used in the above mentioned flood insurance studies. Precipitation data used in the model came 'rom the NOAA Atlas 'or Colorado. Areal adjustment 0' precipitation was made using relationships also in the NOAA Atlas. The duration 0' rain'al I used was 24 hours along with the SCS Type II rain'al I distribution. Time of Concentration values were computed using the 3 flow types (sheet, shallow concent,"ate,j, channel) discussed in SCS Technical Release 55. Data necessary 'or this proceedure came from field reconnisance and map information. Analysis 0' Potential Projects Three conditions were analyzed herein; 1) Future without project, 2) Future with project including only channel i mp,"ovement at the East T," i buta'"y hi ghway-,"a i I road b,- i dges and downstream, 3) Future with project including channel improvements of item 2 accompanied by a flood water retarding dam on the main stem 0' Spring Creek. Table 1 shows peak discharge values 'or these altlernative conditions. Table 2 shows ve,-y p,-el iminary structu,-e data for the proposed flood water retarding structure as developed by the SCS Dams 2 computer program. The 'uture without project condition was analysed using a highway and ,-ai Iroad bridge hyd,"aul ic capacity 0' 500 c's. There is a potential to handle much more 'low than that but sediment and trash deposition and the lack of a downstream channel causes a significant restriction. Condition 2 above provides 'or clearing away 0' the ,-estr i ct ions at the highway and I-a i I road br i dges su" i c i ent tCI a II ow up t.:, 1500 cfs to pass. Condition 3 above provides for the bridge and channel i rnpt~Qvements as we II as a f I Qodwatet- t~etat-d i ng darn. An enclosed map shows the location 0' the proposed dam IStr 01). The dam location was selected on the main stem 0'