Natural Flows with Recharge
When recharge water is part of historical river operations and is to be included in the natural flow calculations, the same natural flow formula is used with the following data:
- Historical diversions (*.ddh) include water from all sources (priority, exchange, etc.) and for all uses (irrigation, municipal, storage, recharge, etc.). This data is commonly called Total Diversion from Headgate.
- StateMod’s Natural Flow module knows the amount of total diversion taken to reservoir storage using a reservoir end-of-month file (*.eom) file. This file that contains reservoir storage data for every reservoir in the system.
- The portion of the total diversions that is taken to recharge is input into the model in the Diversion_To_Recharge (*.dre) file. This file contains total diversions to recharge for every diversion structure that carries water to recharge.
- StateMod’s Natural Flow module adjusts total diversions to account for the portion that is carried to recharge. In order to calculate return flows associated with recharge, a Reservoir_To_Recharge (*.rre) file is provided containing recharge data for every recharge reservoir. This data, along with the reservoir seepage characteristics specified in the reservoir station (*.res) file and return flow properties specified in the reservoir return file (*.rre), are used to calculate accretions from a recharge site.
- The above calculations can be confirmed by reviewing the Natural Flow Base Flow output(*.xbi). The following are noted:
- The column titled Divert is the sum of all upstream diversions included in the historical diversion file (*.ddh). Therefore it includes water from all sources (priority, exchange, etc.) and for all uses (irrigation, municipal, recharge, etc.).
- The column titled Return includes return flows from consumptive uses as well as recharge.
- The column titled Divert to Rech echoes the data provided in the Diversion_To_Recharge (*.dre) file.
- The column titled Reservoir to Rech echoes the data provided in the Reservoir_To_Recharge (*.rre) file.
- When the historical diversion data are adjusted by the amount diverted to recharge, the calculation is not allowed to go negative.
- Diversion_To_Recharge data are only required for a ditch that carries water to recharge. If data are not provided, the diversion to recharge is estimated to be zero. The WDID specified in this file should be the same as the Diversion ID to be adjusted.
- Reservoir_To_Recharge data are only required for a reservoir with recharge. If data are not provided, any accretions or recharge associated with the diversions to recharge are assumed to be zero. The WDID specified in this file should be the same as the Reservoir ID with recharge.