Water Facts 2: 7-Steps for Managing Groundwater Supplies
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http://www.water.ca.gov/pubs/conservation/waterfacts/7-steps_for_managing_ground_water_supplies__water_facts_2_/water_facts_2.pdf
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Number 2
A OF W TER R NT
Water Facts
10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321
Department of Water Resources
DEPART ME
State of California The Resources Agency
TE
O F C A LIF O
7-Steps for Managing Groundwater Supplies
any communities in California use groundwater as the main source for their public water supply system, and many individual residences are totally dependent on groundwater for their supply. In addition, many agricultural operations are partly or entirely dependent on groundwater for their water supply—especially in times of drought. The amount of groundwater in storage in each basin is dependent on the precipitation, recharge and the total extraction of all the wells. A groundwater management plan that is designed for the political, institutional, legal and technical specifics of the basin can help everyone maintain the quality and quantity of the groundwater supply.
M
plan additional programs that will lead to more efficient management. Find out what statutory authority your agency operates under and whether the Water Code provides authority to manage groundwater. Many local agencies are now taking advantage of AB 3030 (California Water Code § 10750, et seq) to develop groundwater management plans for their agency.
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7 Steps
The following 7-step groundwater management program will help local groundwater managers, individuals, residents, and public water supply system operators determine how far groundwater levels will decline if a certain amount of groundwater is extracted. With this information, they will be able to make informed decisions in managing the available groundwater to assure an available supply in the future. Begin your plan now by evaluating the data that are available, even though you think you need more data. This initial evaluation will help you
Water Facts are short reports on water resources issues of general interest. They are published periodically by the California Department of Water Resources and can be obtained free by contacting DWR Bulletins & Reports, P.O. Box 942836, Sacramento, CA 94236-0001; 916/653-1097.
1
Locate and identify water wells, and collect groundwater level and ground water quality data.
The location of each water well in the area should be recorded, and each well should be assigned a "State Well Number" by DWR. Collect drillers' logs, and compile water level measurements and water-quality analyses that are available from each of the wells. Plot this information on maps and graphs for use in steps 2, 3, 4, and 5. This is the start of a monitoring program.
2
Determine the amount of groundwater that is extracted by each well or otherwise removed from the groundwater basin.
Total the amount of groundwater extracted by all wells and add whatever other water is removed from the basin (evapotranspiration, exports, consumptive use, and surface water outflow). Compare this total with the total amount of water that comes into the basin (see Step 4).
February 1996 1
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The amount of water extracted can be measured by water flow or electric consumption meters, or estimated by using the estimated evapotranspiration of each of the crops. (For details, call the DWR telephone numbers listed at the bottom of the next column.)
6
Project future rates of extraction and estimate the rate of decline of ground water levels and possible changes in groundwater quality.
3
• • • • • •
Prepare maps and graphs that show:
Past groundwater levels and groundwater quality; Present or recent groundwater levels, groundwater quality, and rates of ground water extraction; Recent precipitation; Surface water imports; Changes in groundwater levels and groundwater quality; and Water exported from the basin.
Determine the total amount of water that flows into the basin through precipitation and surface water imports and the total amount of water that flows out of the basin.
Use the specific yield values obtained in Step 5 to calculate the estimated change in groundwater level that will occur when an estimated amount of groundwater is extracted. Groundwater quality data can be used to estimate the effect of such extractions on the movement of chemical constituents, either natural or man-caused. Determine whether groundwater extraction is likely to cause subsidence. If yes, prepare a subsidence monitoring program.
7
Develop a plan for managing ground water supplies. Such a plan may require reductions in extractions so the longterm change in storage does not cause water quantity or water quality problems.
4
This is called a water budget. The difference between the inflow and the outflow will result in a change in groundwater level during the water year. If there is more inflow than outflow, groundwater levels will rise. Conversely, if there is more outflow than inflow, as there is during drought years, groundwater levels will fall. Inflow - Outflow = Change in Storage
Such a management plan could include a reduction in the amount of groundwater extracted by specific wells either through a reduced rate of pumping or by restricting the length of time the pump can be turned on. Such reductions would have to be voluntary unless a groundwater management plan is formed implemented by a local agency. Many districts already have some authority to deal with groundwater. For information on how to develop an AB 3030 groundwater management plan or how to form a groundwater management agency, call DWR.
5
Use drillers' logs and other data to estimate specific yield.
For more information, call one of the following DWR Division of Local Assistance offices: Headquarters, Sacramento Northern District, Red Bluff Central District, Sacramento San Joaquin District, Fresno Southern District, Glendale 916/327-8861 916/529-7387 916/227-7590 559/230-3300 818/543-4640
Specific yield is an estimate of the amount of water that is available from an unconfined aquifer. The specific yield can be used to calculate the amount of groundwater in storage, and the decline in groundwater level that will take place when a specified amount of groundwater is extracted by wells (see Step 4).
2
Printed by DWR Reprographics on recycled paper using soy-based inks.
Number 2
A OF W TER R NT
Water Facts
10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321 10987654321
Department of Water Resources
DEPART ME
State of California The Resources Agency
TE
O F C A LIF O
7-Steps for Managing Groundwater Supplies
any communities in California use groundwater as the main source for their public water supply system, and many individual residences are totally dependent on groundwater for their supply. In addition, many agricultural operations are partly or entirely dependent on groundwater for their water supply—especially in times of drought. The amount of groundwater in storage in each basin is dependent on the precipitation, recharge and the total extraction of all the wells. A groundwater management plan that is designed for the political, institutional, legal and technical specifics of the basin can help everyone maintain the quality and quantity of the groundwater supply.
M
plan additional programs that will lead to more efficient management. Find out what statutory authority your agency operates under and whether the Water Code provides authority to manage groundwater. Many local agencies are now taking advantage of AB 3030 (California Water Code § 10750, et seq) to develop groundwater management plans for their agency.
09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 0 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 09876543212109876543210987654321098765432121098765432109876543210987654321 9876543212109876543210987654321098765432121098765432109876543210987654321
7 Steps
The following 7-step groundwater management program will help local groundwater managers, individuals, residents, and public water supply system operators determine how far groundwater levels will decline if a certain amount of groundwater is extracted. With this information, they will be able to make informed decisions in managing the available groundwater to assure an available supply in the future. Begin your plan now by evaluating the data that are available, even though you think you need more data. This initial evaluation will help you
Water Facts are short reports on water resources issues of general interest. They are published periodically by the California Department of Water Resources and can be obtained free by contacting DWR Bulletins & Reports, P.O. Box 942836, Sacramento, CA 94236-0001; 916/653-1097.
1
Locate and identify water wells, and collect groundwater level and ground water quality data.
The location of each water well in the area should be recorded, and each well should be assigned a "State Well Number" by DWR. Collect drillers' logs, and compile water level measurements and water-quality analyses that are available from each of the wells. Plot this information on maps and graphs for use in steps 2, 3, 4, and 5. This is the start of a monitoring program.
2
Determine the amount of groundwater that is extracted by each well or otherwise removed from the groundwater basin.
Total the amount of groundwater extracted by all wells and add whatever other water is removed from the basin (evapotranspiration, exports, consumptive use, and surface water outflow). Compare this total with the total amount of water that comes into the basin (see Step 4).
February 1996 1
N
A
R
IA
RCES OU ES
ST
The amount of water extracted can be measured by water flow or electric consumption meters, or estimated by using the estimated evapotranspiration of each of the crops. (For details, call the DWR telephone numbers listed at the bottom of the next column.)
6
Project future rates of extraction and estimate the rate of decline of ground water levels and possible changes in groundwater quality.
3
• • • • • •
Prepare maps and graphs that show:
Past groundwater levels and groundwater quality; Present or recent groundwater levels, groundwater quality, and rates of ground water extraction; Recent precipitation; Surface water imports; Changes in groundwater levels and groundwater quality; and Water exported from the basin.
Determine the total amount of water that flows into the basin through precipitation and surface water imports and the total amount of water that flows out of the basin.
Use the specific yield values obtained in Step 5 to calculate the estimated change in groundwater level that will occur when an estimated amount of groundwater is extracted. Groundwater quality data can be used to estimate the effect of such extractions on the movement of chemical constituents, either natural or man-caused. Determine whether groundwater extraction is likely to cause subsidence. If yes, prepare a subsidence monitoring program.
7
Develop a plan for managing ground water supplies. Such a plan may require reductions in extractions so the longterm change in storage does not cause water quantity or water quality problems.
4
This is called a water budget. The difference between the inflow and the outflow will result in a change in groundwater level during the water year. If there is more inflow than outflow, groundwater levels will rise. Conversely, if there is more outflow than inflow, as there is during drought years, groundwater levels will fall. Inflow - Outflow = Change in Storage
Such a management plan could include a reduction in the amount of groundwater extracted by specific wells either through a reduced rate of pumping or by restricting the length of time the pump can be turned on. Such reductions would have to be voluntary unless a groundwater management plan is formed implemented by a local agency. Many districts already have some authority to deal with groundwater. For information on how to develop an AB 3030 groundwater management plan or how to form a groundwater management agency, call DWR.
5
Use drillers' logs and other data to estimate specific yield.
For more information, call one of the following DWR Division of Local Assistance offices: Headquarters, Sacramento Northern District, Red Bluff Central District, Sacramento San Joaquin District, Fresno Southern District, Glendale 916/327-8861 916/529-7387 916/227-7590 559/230-3300 818/543-4640
Specific yield is an estimate of the amount of water that is available from an unconfined aquifer. The specific yield can be used to calculate the amount of groundwater in storage, and the decline in groundwater level that will take place when a specified amount of groundwater is extracted by wells (see Step 4).
2
Printed by DWR Reprographics on recycled paper using soy-based inks.
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