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100 years of California's water rights system: patterns, trends and uncertainty

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Title 100 years of California's water rights system: patterns, trends and uncertainty
Title of Series Environmental Research Letters, Volume 9, 2014
Author Grantham, Theodore E.
Viers, Joshua H.
License CC Attribution 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor.
DOI 10.5446/39457
Publisher Institute of Physics (IOP)
Release Date 2014
Language English

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Subject Area Physics
Abstract For 100 years, California's State Water Resources Control Board and its predecessors have been responsible for allocating available water supplies to beneficial uses, but inaccurate and incomplete accounting of water rights has made the state ill-equipped to satisfy growing societal demands for water supply reliability and healthy ecosystems. Here, we present the first comprehensive evaluation of appropriative water rights to identify where, and to what extent, water has been dedicated to human uses relative to natural supplies. The results show that water right allocations total 400 billion cubic meters, approximately five times the state's mean annual runoff. In the state's major river basins, water rights account for up to 1000% of natural surface water supplies, with the greatest degree of appropriation observed in tributaries to the Sacramento and San Joaquin Rivers and in coastal streams in southern California. Comparisons with water supplies and estimates of actual use indicate substantial uncertainty in how water rights are exercised. In arid regions such as California, over-allocation of surface water coupled with trends of decreasing supply suggest that new water demands will be met by re-allocation from existing uses. Without improvements to the water rights system, growing human and environmental demands portend an intensification of regional water scarcity and social conflict. California's legal framework for managing its water resources is largely compatible with needed reforms, but additional public investment is required to enhance the capacity of the state's water management institutions to effectively track and regulate water rights.

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for 100 years California State Water
Resources Control Board and its predecessors have been responsible for allocating available water supplies to beneficial uses but inaccurate and incomplete accounting of water rights has made the state ill-equipped to satisfy growing societal demands for water supply reliability and healthy ecosystems California's Reuter right system is the primary regulatory framework under which the surface water is allocated yet the amount of water actually used by water rights holders is poorly tracked and highly uncertain the lack of accurate accounting thus represents the critical challenge to the allocation of water among competing users in a cost-efficient and sustainable manner here we present the 1st comprehensive evaluation of appropriate of water rights to identify where and to what extent water has been dedicated to human users relative to natural supplies we
analyze the state's water rights database to estimate the degree of water appropriation in
approximately 4 thousand catchments in California by comparing water rights allocation
volumes with mild predictions of unimpaired surface water availability we
found approximately 13 thousand
active appropriate of water rights records accounting for 400 billion cubic meters or 325 million acre-feet of water approximately 5 times the state's mean annual runoff the number of water rights issue has steadily increased since the 20 century following a period of relatively slow growth in the early 19 hundreds the number of rights filed accelerated in the 19 forties although private entities hold the
vast majority of water rights filed here we see that most water by volume is allocated to public entities in fact over 80 per cent of water rights issued by volume are currently held by federal state and municipal and other public entities in the state's major river basins appropriate of water rights account for up to 1 thousand per cent of natural surface water supplies with the greatest degree of appropriation observing tributaries to
the Sacramento and Sandel King rivers in coastal streams in southern California excluding hydropower water use the total volume allocated to privative water rights in the Sacramento-San King delta is approximately 3 times the average unimpaired outflow of the system allocation levels tend to increase was river size although many small rivers particularly on the south coast are also subject to high water demands the phase values of appropriate of water rights reflect the degree to which surface water supplies have been allocated but must be interpreted with caution for example the appropriate of water right system incentivizes permit holders to over report water used to protect the face value amount of their water right and therefore represents a generous estimate of actual water use in addition return flow flow from irrigation runoff or kill leakage
as an example to be reused by downstream appropriators allowing for double counting of the same volume of water
nevertheless the large magnitude of water right allocation volumes relative to natural supplies and poor correlation between
county-level allocations in estimates of actually use provides strong evidence that
the state has overallocated water in many if not most river basins furthermore allocation volumes all the town for post 1914 appropriate of water rights other types of water rights such as preparing claims to make the total amount of surface water allocated significantly higher than estimates provided here without improvements to the water at system growing human environmental demands pretend an intensification of regional water scarcity and social conflict California's legal framework for managing its water resources is largely compatible with needed reforms but additional public investment is required to enhance the capacity of the state's water management situations to effectively track and regular water rights this is a situation that urgently needs correcting to meet California's water management challenges arising from drought population growth and climate change
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