The StateMod model allows ground water pumping via wells to be modeled. See Section 7.7 for more information on how to model well operations. The following are noted:
- Wells are generally operated within StateMod either as an aggregate of wells and their associated water rights tied to a well structure or as supplemental well water rights tied to a surface water diversion structure.
- If a well structure is not tied to a surface water diversion structure then well demands are provided in the well demand file.
- If a well structure is tied to a surface water diversion structure, then demands may be provided and treated in several ways as specified by the control variable
- Wells may increase the water supply available at the river at a given time step if well return flows exceed the stream depletion. StateMod checks for such a condition and reoperates to allow senior ditches to benefit from the additional water supply.
- Wells may require two or more delay patterns to represent the delay associated with return flows and depletions. The data for both types of delays are specified in the delay table input file. Note when the sum of return flows to the river is less than 100%, the balance is treated as a loss. Similarly when the sum of depletions to the river is less than 100%, the balance is treated as salvage.
- Wells may cause river flows to go negative when their estimated depletion to the river exceeds the streamflow. StateMod treats such an occurrence as an
indication that pumping impacts have depleted ground water storage rather than the stream flow. Under such a case, StateMod allows the pumping to occur and
accounts for the source of water as originating from ground water storage. This water is presented in the diversion summary output under the column titled
From/To GW Storfor each river node and for the whole basin in the water budget report (*.xwb). Note the quantity of water supplied by ground water storage in a simulation time period is taken out of the stream the next time period before any water allocation occurs. The control file variable
iwellallows the repayment of this water to be limited to a maximum amount to represent stream / ground water systems that are disconnected. Also, since data for this term is generally not observed, baseflow calculations may be influenced by this lack of data.
- Well information for supplemental wells is presented in four columns of the diversion summary (*.dds) file. The column titled
From Welldescribes the total amount of water pumped and made available to a diversion. The column titled
Well Depletionrepresents the impact of a previous months pumping on the river. The column titled
To/From GW Storwas described above. The column titled
River by Wellrepresents the impact of the current months pumping on the river. The
River by Welldata are separated because the impact of a previous months pumping on the river influences the water supply available to all users before any diversions occur while the impact of the current months pumping impacts water rights that are junior to the well only. In general, the columns titled
River by Wellinclude the impact of all well pumping on the river at any given point in the river.