PUB00052

• Year: 1998
• Title: Layperson's Guide to Groundwater
• CWCB Section: Interstate & Federal
• Author: California Water Education Foundation
• Description: Layperson's Guide to Groundwater
• Publications - Doc Type: Other

In a number of economic and environmental issues,
some say, resources shared in common with few
restrictions are ultimately overused, as all partici-
pants are encouraged to maximize their use and no
participant has an incentive to consider the long-term
consequence of overuse. When the consequences
of over-pumping are severe for at least five years,
groundwater users can ask the court to "adjudicate,"
define the rights that various entities have to ground-
water in the basin. The court can limit pumping to
the "safe yield" of the basin. which is the amount at
water that can be pumped without causing un-
desirable results to the aquifer. Through adjudIca-
tions, the courts can assign specific water rights to
water users and can compel the cooperation of
pumpers who might otherwise refuse to limit their
pumping. Watermasters often are assigned to ensure
that pumping conforms to the limits defined by the
adjudication. Litigation, however, IS time-consuming
and costly, in part because it is difficult to determine
all of the pumpers and their historic pumping
amounts.

WHAT THE COURTS HAVE SAID

One of the first controversies that had to be resolved
was how far water had to seep under a streambed
before It stopped being surface water and started
being groundwater. Early in the 20th century. the
courts divided groundwater into two broad catego-
ries - subsurface flow and percolating groundwater.

Subsurface flow is water moving through the sands
and gravels under or next to a stream channel. Sub.
surface flow is considered to be part of the stream
and subject to the
same riparian and
appropriative rights
that guide the use of
the stream itself. As
a result. the pumping
of subsurface flows,
while constituting
only a small portion
of the groundwater
in California, is regu-
lated by the State
Board.

Percolating water is
often defined as
water moving through
the soil by gravity
along the path of
least resistance. In
California, the term
covers the vast
majority of ground-
water. And with few
exceptions, the State
Board does not gov-
ern the use of percolating water. The legal distinc-
tion, however, is a sharper line than the hydrological
distinction. As a result, determining when water fits
into each category has been a source of controversy
in some water disputes.

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A 1903 ruling established that for landowners over-
lying an aquifer, each property had a "correlative" or
co-equal right to a "Just and fair proportion" of the
resource. That standard is different than the one
governing surface water rights, which limits the
amount of water that can be used and establishes a
priority system for allocating water during shortages.
Correlative rights. while acknowledging that
shortages may occur, only require that all property
owners share equally in the resource until it is
exhausted - irrespective of the consequences.

8

Through this process. the courts have adjudicated
16 basins in California. One of them is near the
Oregon border. the Smith River system. where
groundwater was adjudicated to help resolve a
surface water controversy. Another is the Santa
Margarita River watershed. where the court did not
limit pumping. The remaining 14 adjudications have
all been in southern California, where development
pressures quickly overwhelmed limited aquifers:
Central Basin, West Coast Basin. Upper Los Ange-
les River Area (San Fernando). Raymond Basin.
Main San Gabriel Basin, Cummings Basin.
Tehachapi Basin. Warren Valley Basin. Chino Basin,
Cucamonga Basin, Puente Basin, Mojave River
Basin, the San Bernardino Basin and the Santa
Paula Basin.

In adjudicating these basins, early court decisions
affirmed the concept of correlative rights and estab-
lished two other kinds of groundwater entitlements.
If water is available after the needs of property
owners have been satisfied. the courts have allowed
for water to be pumped and exported from those
lands by an appropriative user. The courts ruled that
among appropriators, the first to pump has the first
entitlement to export water. When it is necessary to
limit pumping by appropriative users, those limits
should be based on how much the users pumped
historically. Creating limits based on past use.
however, provides an incentive to pump more water