How to Implement the Maximum or Mutual Supply Approaches

StateMod allows the user to simulate wells using a Maximum or Mutual water supply approach. Both require an irrigation parameter (*.ipy) file be provided that contains total ground water acreage, sprinkler acreage, efficiency data, and water use approach parameter (gwmode = 1 or 2) which controls whether Maximum or Mutual Supply will be used. Additionally, both options require variable efficiency to be turned on in the control (*.ctl) file (ieffmax = 1). Both approaches operate from senior to junior using water right data provided.

For the Maximum Supply approach, an operating rule allows the water right priority of wells associated with lands served by sprinklers to be made senior in order to apply water to lands served by sprinklers before any other source. To enable this functionality:

1. Open the control (*.ctl) file in a text editor and set the isprink parameter to 1. Additionally, confirm variable efficiency is being considering by verifying the itsfile parameter is set to 10 and the ieffmax parameter is set to 1.
2. Set the water use approach variable (gwmode) in the irrigation parameter (*.ipy) file to 1 to indicate the maximum supply option.
3. If appropriate, verify that acreage served by sprinkler and/or ground water supplies is not zero. If the acreage served by sprinklers is zero or no ground water acreage is included, then sprinklers cannot be operated at a senior priority.
4. Include a Type 21 operating right where the administration date reflects a senior value that will cause wells with sprinklers to operate first.

For the Mutual supply approach there is no operating rule required and wells operate according to the priority provided in the well water right file.

1. Open the control (*.ctl) file in a text editor and set the isprink parameter to 1. Additionally, confirm variable efficiency is being considering by verifying the itsfile parameter is set to 10 and the ieffmax parameter is set to 1.
2. Set the water use approach variable (gwmode) in the irrigation parameter (*.ipy) file to 2 to indicate the mutual supply option.
3. No operating rule is necessary.

During a natural flow simulation, operating rule data is not read. Therefore natural flows are calculated using a Maximum Supply approach if the irrigation parameter (*.ipy) file variable gwmode is set to 1 and the control file (*.ctl) variables are set as follows: itsfile = 10, ieffmax = 1, isprnk = 1. If any of the above are not set appropriately the Mutual Supply approach is used.