Agricultural runoff is one of the primary sources of discharge to rivers and streams that do not meet water quality standards, affecting 70 percent of these impaired waters. This problem is particularly challenging in the western United States, where roughly 50 million acres of land are devoted to irrigated agriculture and where agricultural drainage and runoff provide a significant proportion of river flows during dry seasons.
The Grassland Drainage Area is an agricultural region on the west side of California's San Joaquin Valley. The agricultural land there is productive, but the soil contains a high level of selenium, a naturally occurring trace element. Selenium accumulates in the agricultural drainage water that collects in the tiles installed to drain excess water from the fields. In 1983 this problem received national attention when deaths and deformities in wildlife at the Kesterson Reservoir were attributed to selenium-contaminated drainage from outside the Grassland Drainage Area. In the early 1990s, selenium-laden drainage from the Grassland Drainage Area was still being discharged into other federal and state wildlife refuges, threatening important ecosystems and associated fish and wildlife.
An innovative tradable loads program
The Grassland Bypass Project is an innovative program designed to improve water quality in the channels used to deliver water to wetland areas. In 1996 several irrigation and drainage districts formed the "Grassland Area Farmers," a regional drainage entity that includes some 97,000 acres of irrigated farmland.
The group's initial goal was to use the San Luis Drain, owned by the federal Bureau of Reclamation, as an outlet for agricultural drainage. To do so, they entered into a Use Agreement with Reclamation, incorporating monthly and annual selenium load limits. A procedure was included in the Use Agreement to assess incentive fees if the monthly or annual load limits were exceeded. In addition, a maximum cap was established on the total amount of selenium that the Grassland Area Farmers could discharge. The Use Agreement for the project continued until September 2001, at which time development of a long-term plan began.
To meet the selenium load limits, the Grassland Area Farmers have implemented a wide variety of practices, including formation of a regional drainage entity, newsletters and other communications with the farmers, a monitoring program, an active land management program to use subsurface drainage on salt-tolerant crops, installation of improved irrigation systems, installation and use of drainage recycling systems to mix subsurface drainage water with irrigation supplies under strict limits, and tiered water pricing.
Additionally, with support of section 319 funding, the Grassland Area Farmers developed and adopted a "tradable loads" program to help achieve regional water quality targets. To date, pollution trading policies have been designed for trades between point sources, such as factories, and trades between point sources and nonpoint sources, such as farms. This project is unique in that it also establishes a trading program between nonpoint sources.
Under the tradable loads program, the total allowable regional selenium load is allocated among the member irrigation and drainage districts. The districts can then either meet their load allocation or buy/trade selenium load allocation from other districts. The theory is that the region will meet its selenium load target at the lowest possible cost because reduction measures will be taken where they are cheapest to achieve. In addition, the program should spur innovation by bringing selenium reduction decisions to a more localized level. Finally, the tradable loads program aims to distribute the costs of selenium discharge reduction equitably among the districts.
The environmental benefits of the project to wetland areas, including state and federal refuges, are significant. Drainage water has been removed from more than 93 miles of conveyance channels, allowing for delivery of fresh water to the wetland areas. Good-quality water from areas upslope of the Grassland Drainage is now separate from selenium-contaminated drainage water and can be put to use in the Grassland Water District and in the state and federal refuges.
Compared to data on preproject conditions observed in 1996, year 2000 data reflect that drainage volume has been reduced 41 percent; selenium load, 54 percent; salt load, 29 percent; and boron load, 14 percent. With the exception of the very wet year 1998, data show a continuous reduction in selenium discharge since 1995reductions from 16 ppb to 2 ppb in some channel segments and reductions from 55.9 ppb to an average of 2 ppb in others. Selenium load targets were met every month in 1999 and 2000 and have been met every month to date in 2001. Selenium loads in 1999 and 2000 were the lowest ever discharged from the drainage in the past 15 years.
Other related efforts
The tradable loads program works together with other policies in place in the Grasslands Drainage Area. Many of the programs designed to encourage water conservation through irrigation efficiency also decrease selenium discharge. For example, one of the member districts of the Grassland Area Farmers pioneered a tiered water pricing policy in which increasing block-rate pricing motivates the use of water conservation practices. Other districts in the Grassland Drainage Area have followed suit by implementing their own tiered water pricing policies.
Additional incentive-based water conservation programs in the Grassland Drainage Area include low-interest State Revolving Fund loans and land management incentives. Irrigation system improvements in the Grassland Drainage Area include quarter-mile furrows, gated pipe, sprinklers, and drip irrigation systems. Districts are also pursuing methods aimed directly at selenium reduction.
In addition to providing local water quality benefits, this project provides valuable insight for controlling agricultural nonpoint source discharges elsewhere. Through a combination of quantitative discharge limits and economic incentives, a model that provides for direct accountability within a system that is locally controlled is emerging. In the long term, the use of economic incentives might enhance implementation by promoting cost-effectiveness and preserving farmers' flexibility to choose the most appropriate pollution reduction practices.