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Groundwater Groundwater resources playa vital role in California and have and will continue to be an integral part of water transfers. Groundwater provides about one- third of California's supply on average and as much as two.thirds in dry years. Hydrologically, ground- water is inseparable from surface water resources. Precipitation soaks into the earth and becomes groundwater or later resurfaces as a spring, stream or spring-fed lake. It is estimated as much as 30 percent of the state's surface water comes from groundwater. Overlooking the interconnection of groundwater and surface water could lead to an involuntary redistribution of surface water. Transfers that involve groundwater must take into account not only the physical difference of the resource but also a separate set of laws and judicial decisions that affect its use. In spite of the impor. tance of groundwater, its use in California is gener- ally unregulated. There is no statewide compre- hensive groundwater management plan and perco- lating groundwater, which is the bulk of the resource, is not regulated. State law does require that groundwater use be reasonable. Groundwater can be appropriated like surface water but there is no permit process. There are general parameters that apply to property owners above a groundwater aquifer. Property owners overlying an aquifer have a reciprocal right to a fair amount of the resource, or a "correlative" right. Overlying rights are analogous to riparian rights and are not quantifiable unless the groundwater basin has been adjudicated, a process that establishes the rights of the affected parties. The rights of landowners of overlying land are superior to groundwater appropriator rights and only surplus water is available for appropriation by others under the first in time, first in right rule. Transfers of groundwater can threaten the integrity of a groundwater basin. Excessive pumping and insufficient recharge will cause overdraft, which can lead to a range of problems including lower water tables, increased pumping costs, land subsidence and reduce water quality caused by contamination from intrusion of sea water and/or other sources. DWR drought water banks bought and sold surtace water that was substituted with groundwater but raised concerns from some area residents. After 1991 withdrawals, some Yolo County residents telt the additional pumping aggravated existing overdraft and land subsidence. According to DWR, which monitored groundwater pumping in three counties, the increased pumping did not cause significant adverse impacts. Likewise, a group of local Butte County farmers near the Western Canal Water District claimed that added pumpong of the aquifer to replace transferred surface water, in 1994, lowered water tables, which increased pumping costs and threatened local crops. State law allows surface water to be sold and replaced with groundwater but requires pumping to be consistent with a groundwater management plan if one is in place, or otherwise be approved by the local water district. In addition. transferors who sell surface water cannot replace it with groundwater if the groundwater substitution would cause or aggravate overdraft in a groundwater basin. .:tl~~;;,\"...,,,., To protect ground- water in unregu- lated basins, legis. lation was passed in 1992 that allows water agencies to develop ground. water manage- ment plans. The law, however, does not require the plans to include the entire county, groundwater basin or watershed, and watersheds often cross political boundaries. In addition, cities within counties can adopt their own management plans, and many plans have faced formidable opposition because of fears of pumping restrictions and pump taxes. County ordinances have been passed in a number of counties to protect local groundwater from over- draft, particularly from out-of-county exports. A county's authority to regulate its groundwater supplies was established in late 1994 by an appellate court in Baldwin v. Tehama County. The case arose alter two farmers, who owned land in Tehama County and wanted to export groundwater to another county, sued Tehama County after it enacted an ordinance to protect groundwater resources. The 1992 ordinance restricted new groundwater wells and required permits for transfer of groundwater outside the county. An appellate court ruled that counties have the authority fo regulate groundwater under their police power. . ~. """'~~'... -"'-,. ';'. --~. . ~ '.- ..~~.-.-,,~ .....1. - _ ".J -~ Tram/en; that il/\'olve groundwater must rake iwo account not only the physical difference oj the resource but a/so a separate set of laws and jlldicial decisions that a..ffect its use. 15