CRDSS_Task1_15-12_DataManagementInterfaceToEstimateMonthlyNetReservoirEvap

• Title: CRDSS Task 1.15-12 - Water Rights Planning Model - Data Management Interface to Estimate Monthly Net Reservoir Evaporation
• Description: This task memorandum documents the design considerations of the data management interface ‎(DMI)‎ that will estimate the net monthly evaporation for a reservoir.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/9/1995
• DSS Category: Surface Water
• DSS: Colorado River
• Basin: Colorado Mainstem
• Contract/PO #: C153658, C153727, C153752
• Grant Type: Non-Reimbursable
• Bill Number: SB92-87, HB93-1273, SB94-029, HB95-1155, SB96-153, HB97-008
• Prepared By: Riverside Technology inc.

from a single precipitation station (PrecipStaID) with a corresponding weighting factor of 1.0. The net
evaporation time series will be estimated from two evaporation stations (EvapStaID1, EvapStaID2) with
corresponding weighting factors of 0.70 and 0.30 using a pan coefficient of 0.75 for both stations.
netresev TaylorPk -mo -in -1 -.80 PrecipStaID -1.0 EvapStaID1 -.70 -.75 EvapStaID2 -.30 -.75
The water rights modeling group will identify the reservoirs that are modeled in each basin.
The DMI utility will create the monthly net evaporation for a specified reservoir using the historical data
for pan evaporation and precipitation at the specified meteorological stations. The procedure to estimate
monthly net evaporation is outlined in the following steps.
1.If a single precipitation station is specified, the historical time series for that station will be used in
step 3. If more than one precipitation station is specified, the following equation will be used to
estimate a single time series from the precipitation data at each station.
N
M APWCP
Equation 1
jiij
=
i 1
where MAP is the mean areal precipitation,
WC is the weighting factor for station i,
P is the point precipitation for station i, month j, and
N is the total number of specified precipitation stations.
2.If a single evaporation station is specified, the historical time series for that station will be used in
step 3. If more than one evaporation station is specified, the following equation will be used to
estimate a single time series from the evaporation data at each station.
M
E VAPWCPCE
Equation 2
jiikj
=
iM
where EVAP is the mean areal evaporation,
WC is the weighting factor for station i,
PC is the pan coefficient for station i,
E is the point evaporation for station i, month j, and
M is the total number of specified evaporation stations.
3.A single net evaporation time series will be created by subtracting the mean areal precipitation time
series from the mean areal free surface evaporation time series.
Equation 3 NETEVAPAEVAPBMAP
jj j
3
A275 01.09.95 1.15-12 Ritsch