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<br />TABLE 3. Historic Peak Flows <br /> <br />3.3 Stte~m Gaqe Data <br /> <br />A hydrologic analysis was performed to determine 100-year <br />peak flows on streams in Costilla County. The principal data <br />sources were the USGS publication. Technical Manual No. I, <br />Manual for Estimatino flood Characteristics of Natural-Plow <br />Streams in eolor~do (TM-I). pUblished in 1976. ~nd a USDA Soil <br />Conservation Service (Ses) hydrologic analysis for the Town of <br />San Luis. prepared as a part of a 1979 flood control project <br />study that was conducted by the SCS. These two sources were, <br />in turn. principally b~sed on analyses of qaqe records for <br />sites in Costilla county. <br /> <br /> Location Recorded <br />Stredm Date flow <br />Rio Grande Near Lobatos 6/8/0~ 13,200 ", <br />Rio Gr~nde Ne~r Lasauses 6/21./49 5,470 ", <br />Trincher~ Creek Below Smith 5/11/42 1.320 ", <br /> Reservoir <br />Trincheri:l Creek Above Mountain 5/11/<:7 m ," <br /> Home Reservoir <br />Trinchera Creek Near Fort 5/27/42 '" ", <br /> Garland <br />Sangre " Cristo Near Fort 8131/38 1.520 ,', <br />Creek Garland <br />U<o Creek Near Fort 5/15/41 '30 ", <br /> Garland <br />Culebrd Creek Below 5/30/42 '" ", <br /> "0 Luis <br />CUlebra Creek ^' San Luis 7/1/47 OS< ,', <br />Costilla Creek ^' Gu:cia 5/11/42 1,000 of, <br />Costilla Creek Above 7/22/54 3.870 ," <br /> Costilla Dam. <br /> New Mexico <br /> <br />TM-l included gage IInalyses for five (5) stream gages in <br />Costilla County. These gages are listed in Table 4. The SCS <br />analyzed five {5} g~ges also. Three of those gages had already <br />been analyzed in TM-l. The results of their analyses are <br />listed in Table 5. <br /> <br />Since it had not been analyzed for TM-I or the SCS study, <br />one more gage was studied by the CWCB. The gage on Trinchera <br />Creek below Smith Reservoir was felt to be important because it <br />had over 50 years of record and because it provided data <br />further downstream on any Of the three major tributaries than <br />any other gage in the county. Even though it is located below <br />a reservoir. the gage provided helpful data. <br /> <br />The site is actually downstream of two reservoirs. Mountain <br />Home Reservoir is upstream of Smith Reservoir on the mainstem <br />of Trinchera CreeK (see Figure 4). Sanqre de Cristo Creek does <br />not flow tnrough Mountain Home Reservoir. but joins Trinchera <br />CreeK at Smith Reservoir, farther downstream. Sangre de Cristo <br />Creek actually contributes a much larger drainage area to the <br />Trinchera Cree~ basin above Smith Reservoir than does the <br />Trinchera Creek mainstem. <br /> <br />I <br />" <br />I <br />" <br /> <br />The question Of what role either of these reservoirs might <br />play in flood l:lows on Trichera Creek c-'n. however, be put <br />aside. As is discussed in Section 3.4 (Reservoirs). ultimately <br />no flood storAge credit was given to any Of the reservoirs in <br />Costilla County for the purposes of this study. 61 square miles <br />on the trinchera Cree~ mainstem are tributary to Mountain Home <br />Reservoir. these were not subtracted from the total drainage <br />area at the qage below Smith Reservoir (396 square miles). The <br />calculilt..d 100-year flow of 1.560 c.f.s.. based on thi' <br />assumptions described in Section 3.4. provided useful <br />information for the discharge profile for Trinchera Creek west <br />of the foothills. <br /> <br />, <br />, <br /> <br />Add~tionally one gage that had been ar.alyzed fo: TM_l. the <br />qaqe on Costilla Creek above Costilla Dam in Ne~ Mexico, ~as <br />restudied by the CWCB. For :easons that are unclear. several <br />years Of tecord on that stream. includinq an exceptionally <br />large flo~ in 1954. were not made part of the TM-l analysis. <br /> <br />-19- <br /> <br />-20- <br />