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San Joaquin Valley Agricultural Drainage

Introduction
Chronic problems of salt, selenium, boron and other naturally occurring elements in surface and groundwater supplies plague agricultural regions throughout the Westside of the San Joaquin Valley. Compounding the problem is the build-up of salty subsurface groundwater resulting from dense clay layers and inadequate natural drainage.

The Integrated On-Farm Drainage Management (IFDM) system was developed to manage these problems. A state-of-the-art, yet practical management system, the IFDM manages irrigation water on salt-sensitive high value crops and reuses drainage water to irrigate salt-tolerant crops, trees and halophyte plants. Salt and selenium are removed from the farming system and can be marketed. This system views the subsurface drainage water containing salts and selenium as resources, rather than considering them as wastes and environmental problems.

Simply stated, the grower sequentially reuses drainage water to produce crops with varying degrees of salt tolerance. A solar evaporator receives the final volume of drainage water; this water evaporates and salt crystallizes. Plants absorb selenium, which may be volatilized; or accumulate in the plant tissue. Of the remaining selenium some will remain in the soil and some will be contained in the final effluent to become a component of harvested salt. There is no discharge of salts and selenium into rivers or evaporation ponds. Drainage water, salts and selenium are managed on the farm.

An IFDM system can serve as a viable alternative for landowners who may not choose to participate in a voluntary land retirement program for drainage-impacted lands. Once the irrigation systems have been optimized to maximize water use effeciency and to minimize the production of subsurface drainage water, an IFDM system can be designed to enable the landowner to process the resulting drainage water on-farm.

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Salt Management
Farming in high saline areas limits farmers' options on how they manage the accumulation of salt on productive farmland. The options are variable and depend on the physical conditions within the farm boundaries and the farm economics. The key to any drainage management program is improved irrigation efficiency.

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Components of an IFDM System
The system may consist of border strips of trees to intercept regional groundwater flow, three distinct crop production areas, each with its own subsurface drainage system and sump, sump pumps and piping to move the collected subsurface drainage water to each of the cropping areas, and a solar evaporator.

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Monitoring
Water quality monitoring and the subsequent recordkeeping practices are important components of a successful IFDM program. A properly designed monitoring program will aid in assessing any impact of the agricultural drainage water disposal on surface and groundwater quality, fish and wildlife, and public health.

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Plant Selection
Over the past decade, research and informal testing by university, government and resource agency personnel have identified a large number of salt-tolerant agronomic crops, forages, halophytes and trees that can be used in IFDM plantings.

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Wildlife Issues
A goal of IFDM is to dispose of highly saline agricultural subsurface drainage water in an environmentally sound way that does not impact wildlife. Avoidance measures to greatly reduce the negative impacts on wildlife include the design and management of the solar evaporator.

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Economics
Although the cost of planning and implementing an IFDM system may be high, the potential for economic gain and to continue farming may be higher. The benefits from an IFDM strategy include the ability to produce higher value crops and manage salinity and groundwater levels, while complying with regulations.