Existing law declares that all water within the state is the property of the people of the state, but the right to the use of the water may be acquired by appropriation in the manner provided by law. Existing law requires the appropriation to be for some useful or beneficial purpose. Existing law provides, however, that the diversion of floodflows for groundwater recharge does not require an appropriative water right if certain conditions are met, including that a local or regional agency that has adopted a local plan of flood control or has considered flood risks as part of its most recently adopted general plan has given notice, as provided, of imminent risk of flooding and inundation of lands, roads, or structures. Existing law defines “floodflow” for these purposes, to include circumstances in which flows would inundate ordinarily dry areas in the bed of a terminal lake to a depth that floods dairies and other ongoing agricultural activities, or areas with substantial residential, commercial, or industrial development. Existing law defines “imminent” for these purposes to mean a high degree of confidence that a condition will begin in the immediate future. Existing law also requires the person or entity making the diversion for groundwater recharge purposes to file with the State Water Resources Control Board and any applicable groundwater sustainability agency for the basin, a notice containing specified information no later than 48 hours after initially commencing diversion of floodflows for groundwater recharge, a preliminary report no later than 14 days after initially commencing that diversion, and a final report no later than 15 days after the diversions cease. These requirements apply to diversions commenced before January 1, 2029.

This bill would, among other things, expand the conditions that are required to be met for the diversion of floodwaters for groundwater recharge that do not require an appropriative water right. The bill would expand the definition of “floodflow” to include flows that are projected by the local or regional agency to inundate ordinarily dry areas in the bed of a terminal lake, as described above. The bill would revise the definition of “imminent” to mean a high degree of confidence that a condition will begin or is projected to begin within the next 72 hours. The bill would require that a local or regional agency with the responsibility for flood management take specified actions, including making a declaration that diversion of floodflows for groundwater recharge from a delineated stretch of waterway within its jurisdiction is in accordance with one of certain enumerated plans relating to flood control or flood risk, as specified, or a local hazard mitigation plan under specified federal law, and to give public notice, as specified, that a delineated area within the local or regional agency’s jurisdiction is at imminent risk of flooding and inundation of land, roads, or structures. The bill would require diversions to cease no later than 30 days after the public notice is given, unless they are renewed. The bill would require, not less than 48 hours from the projected end of flood conditions, a local or regional agency that has made a declaration authorizing flood diversions to issue a declaration when flood conditions are projected to end informing the public and diverters when diversions shall cease, as provided. The bill would further require, within 24 hours of the declaration, that agency to post the declaration and forward the declaration to all diverters that have informed the agency of diversion.

This bill would also require an entity making the diversions for groundwater recharge that is required to file the notice and the reports, including the final report, as described above, with the board and the applicable groundwater sustainability agency for the basin, to also file those documents with the agency that issued the applicable flood determination. The bill would require the final report to contain information, if applicable, describing the forecasting models used to determine a likely imminent escape of surface water and a description of the methodology used to determine the abatement of flood conditions. The bill would further require the board to post the notice and the reports on the board’s internet website on the next business day after receipt. The bill would require that temporary floodflow diversions be consistent with the most junior priority relative to all water rights holders in the watershed and prohibit those diversions from injuring a prior water rights holder.

Existing law imposes a condition, pursuant to the provisions described above, applicable only to diversions from water tributaries to the Sacramento-San Joaquin Delta (Delta), that the diversion of floodflows for groundwater recharge does not require an appropriative water right if water rights holders are not making releases of stored water or reoperating facilities to provide flow for the purposes of meeting water quality control plan or endangered species requirements in the Delta at the time of the diversion.