SPDSS_Task81-2_Consumptive Use and Water Budget Technical Peer Review Meeting Follow-Up

Home Browse Search

• Questions were asked about missing climate data and filling of that data. (Mike Sayler, Duane Helton) Response (Beorn) was that filling methods were consistent with NOAA practices and described in the memos. Reservoir Evaporation Estimates • Consider using FAO 56 Publication method (PM reference ET based) of determining reservoir evaporation. (Ivan Walter) Ivan indicated that he believes that NOAA Technical Report NWS 34 overstates actual reservoir evaporation and it is his opinion that reservoirs may act as a heat sink, which would reduce evaporation. • Dick Wolfe indicated that the SEO has looked at NOAA mapping and showed it is reasonable. • Jon Altenhofen believes the evaporation rates used in the NCWCD ModSim model are documented in the TriHydro report. Potential Consumptive Use Estimate Review • No comments. Effective Precipitation Estimates • No concern voiced regarding the use of the TR-21 method during the irrigation season. • Prior CDSS efforts have not considered non-irrigation season precipitation, although StateCU has the ability to consider a percentage of winter precipitation as effective. • If considering non-irrigation precipitation, accounting must separate consumptive use from winter precipitation versus consumptive use from irrigation water in the soil moisture reservoir. (Bruce Kroeker) • When considering winter precipitation, one also needs to consider winter ET. By ignoring both, they may balance each other out. (Duane Helton) • Denver Water's South Park study showed that around 34% of winter precipitation is effective at high altitudes and a study conducted near Akron by Grub showed that about 30% of winter precipitation is effective. (Ivan Walter) • Consider running StateCU analysis with and without winter effective precipitation and compare differences. (Erin Wilson) High Altitude Blaney-Griddle Crop Coefficients • Due to the high elevation and lack of potential CU in the shoulder months of the irrigation season, the Denver Water South Park study did not develop high altitude coefficients for the months of April and October. What will SPDSS do for high altitude coefficients in shoulder months when applying the South Park coefficients at lower elevations such as 7,000 feet? (Ivan Walter) At this point in time, SPDSS considers CU in the shoulder months, even in the lower elevations, to be minimal and believe it can be zeroed out. Ivan agreed with this concept. SPDSS may want to evaluate the affects of this concept. (Ross Bethel) • Ivan Walter expressed concern about applying the South Park coefficients at lower elevations such as Salida, do to such things as different growing seasons. • The high altitude (above 6500') portion of the SPDSS area includes less than 1% of the total SPDSS irrigated acreage in 2001. (Erin Wilson) Note that this percentage will be Page A3 of AS