SPDSS_Task53-3_Assign Key Climate Information to Irrigated Acreage and Reservoirs

• Title: SPDSS Task 53.3 - Assign Key Climate Information to Irrifated Acreage and Reservoirs
• Description: This memorandum presents the general approach for the following Task 53 subtasks: 1. Assign key climate stations to geographic areas for the SPDSS modeling efforts. 2. Estimate average monthly reservoir evaporation rates for geographic areas.
• Decision Support - Doc Type: Task Memorandum
• Date: 2/1/2006
• DSS Category: Consumptive Use
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153954
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: Leonard Rice Engineering

Table 5
Estimated Average Monthly Total Precipitation
(Inches)
Water District Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
1-Upper 0.36 0.37 1.08 1.66 2.26 1.92 2.49 2.54 1.19 0.86 0.65 0.40 15.79
1-Lower 0.23 0.18 0.73 1.12 2.09 2.10 2.31 1.82 1.23 0.69 0.38 0.24 13.15
2 0.41 0.34 0.97 1.56 2.44 1.76 1.43 1.17 1.14 0.87 0.68 0.37 13.14
3-Upper 0.68 0.81 1.78 2.33 2.68 2.06 2.58 2.13 1.64 1.12 1.12 0.66 19.61
3-Lower 0.44 0.36 1.03 1.66 2.60 1.88 1.52 1.25 1.22 0.92 0.73 0.40 14.01
4-U er 0.55 0.75 1.51 2.13 3.17 2.53 3.33 2.98 1.90 1.22 0.97 0.69 21.73
4-Lower 0.43 0.42 1.22 1.84 2.62 1.76 1.17 1.35 1.35 0.90 0.75 0.49 14.30
5-Upper 1.32 1.25 2.38 2.85 3.18 2.21 2.70 2.62 1.94 1.35 1.60 1.24 24.63
5-Lower 0.44 0.43 1.25 1.88 2.68 1.79 1.19 1.38 1.38 0.92 0.77 0.50 14.60
6-U er 0.90 0.96 1.98 2.55 2.74 2.12 3.16 3.51 2.02 1.42 1.27 1.12 23.74
6-Lower 0.55 0.67 1.52 2.07 2.67 1.73 1.54 1.41 1.41 1.06 1.04 0.59 16.27
7-Upper 0.83 0.89 1.83 2.37 2.54 1.97 2.93 3.25 1.87 1.31 1.18 1.04 22.02
7-Lower 0.49 0.55 1.33 1.87 2.58 1.89 1.71 1.59 1.32 0.95 0.92 0.51 15.72
8-Upper 0.41 0.58 1.28 1.56 1.94 1.61 2.44 2.51 1.17 1.00 0.76 0.54 15.81
8-Lower 0.50 0.60 1.35 1.59 2.24 1.75 2.07 1.88 1.13 0.94 0.79 0.55 15.40
9-U er 0.59 0.91 1.85 2.40 3.04 2.32 2.52 2.56 1.62 1.34 1.07 0.75 20.97
9-Lower 0.49 0.55 1.34 1.89 2.60 1.91 1.73 1.60 1.33 0.96 0.93 0.51 15.86
23 0.28 0.39 0.78 1.02 1.52 1.67 2.98 3.36 1.46 1.01 0.51 0.42 15.39
47 1.02 0.96 1.21 1.60 2.32 1.91 2.35 2.25 2.03 1.46 1.30 1.03 19.45
48 0.78 0.93 2.06 2.69 3.10 2.38 2.98 2.46 1.89 1.30 1.30 0.76 22.64
64 0.30 0.28 0.80 1.22 2.70 2.57 2.49 1.71 1.08 0.87 0.48 0.29 14.79
76 0.64 0.76 1.67 2.19 2.52 1.94 2.42 2.00 1.54 1.06 1.06 0.62 18.41
80 0.45 0.65 1.46 2.09 2.45 1.90 3.03 2.99 1.56 1.29 0.87 0.62 19.35
Step S: Estimate average net monthly evaporation rates
Average monthly net reservoir evaporation was calculated as the difference between gross
reservoir evaporation and total precipitation (Table 6). Total precipitation can exceed gross
reservoir evaporation, resulting in a negative net reservoir evaporation (a net addition to the
reservoir). When this occurs under water rights applications, the net evaporation is estimated to
be zero (a credit is not given for negative net evaporation). However, because these estimates
are being used in the SPDSS to represent physical conditions for modeling purposes, negative
net evaporation values are used.
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