The survey data set provides data over a five-year period from 1987 to 1991, and State Controller financial data is available over this same time period. A pooled-time series analysis would likely provide a richer view of how districts manage their finances over a longer period, particularly given the apparent large fluctuations in net income and availability of “other non-operating income.” Changes in cropping patterns, water use and water rates over this period also is available in the survey data set. The State Controller data set also contains information on district debt loads and infrastructure investment, and financial data on other district activities such as flood control and electricity production. How electoral rules might influence these decisions might affect at least indirectly the differential reliance on operating versus non-operating revenues. The first set is the year in which the district was founded,procona system and the dates that the district began receiving water service from either of the large water projects, i.e., the Central Valley Project or the State Water Project. These date could be useful in sorting out whether the differences seen between districts is more reflective of electoral rules or of the contractual arrangements offered by the project managers, i.e., the U.S. Bureau of Reclamation and the California Department of Water Resources.

The question is whether a particular political form conforms best with the contractual needs or that a contractual and investment arrangement dominates whatever electoral form was chosen. The problem is likely to be endogenous and require a more sophisticated econometric analysis than presented here. The second set would come from overlaying locally-specific groundwater usage and depth data available from the CDWR’s CVPM mathematical-programming model. Data on “discrete analytic units” shows estimated groundwater usage rates and depth by local regions that usually encompass several districts in the Central Valley . Combined with the surface-water source data, the total water usage within a district could be estimated and compared. A closer review of CVP and SWP deliveries to these specific districts also would be useful to derive a more accurate estimate of water consumption. A third set would incorporate the soil type information also included in the CVPM model and shown to have a significant effect on the choice of irrigation technology and water application rates . This information would help further distinguish between district characteristics.The Pajaro River and Elkhorn Slough watersheds on California’s Central Coast include some of the state’s most productive and highly valued agricultural lands. The watersheds’ streams and rivers serve as key municipal and agricultural water sources, recreational areas, and wildlife habitat. Both watersheds drain into Monterey Bay, a nationally protected marine sanctuary, and water from the Elkhorn Slough watershed passes through Elkhorn Slough, the largest tidal salt marsh along the Central Coast and a critical resource for resident and migratory birds, fisheries, and other wildlife.

Agricultural and urban land uses in the Pajaro River and Elkhorn Slough watersheds have compromised the quality of their waterways. Two nutrients, nitrogen and phosphorus , are of particular concern. High levels of nitrate-N in drinking water pose a threat to human health, and both nitrogen and phosphorus are linked to excessive growth or “blooms” of algae and other plants that can decrease the amount of dissolved oxygen in waterways below the levels that aquatic organisms need to survive. As part of state and federal efforts to protect and restore water quality, regulatory agencies have been charged with establishing target concentrations for pollutants in waterways that will protect beneficial uses1 . The Central Coast Regional Water Quality Control Board has set a preliminary target of 0.12mg/L for soluble reactive phosphorus concentrations, based on the lowest concentrations they have observed in waterways of the Pajaro watershed with excessive plant or algae growth. This pollution is thought to come primarily from “non-point” sources, which are unregulated discharges from urban and agricultural land uses. Most growers along California’s Central Coast use phosphorus fertilizer to maintain high crop production. Increasing evidence suggests that crops cannot take up all of the phosphorus fertilizer being applied ; as a result, excess phosphorus accumulates in the soil. High levels of soil phosphorus in turn lead to higher phosphorus levels in water draining from agricultural fields . In the Pajaro River and Elkhorn Slough watersheds, high concentrations of phosphorus have been identified in several waterways. The RWQCB Watershed Management Initiative implicates agriculture as the primary source of this and other nutrient pollution . However, little empirical data exists to demonstrate that agriculture is responsible for nutrient loading into these waterways.

In this research brief we present data from water quality monitoring conducted between October 2000 and September 2004, to demonstrate the way that agricultural land use influences phosphorus concentrations in streams and rivers. We discuss the nature of phosphorus pollution from agriculture along the Central Coast, examine the implications of these data for agricultural regulations, and offer suggestions for reducing phosphorus losses from farmlands.The Pajaro River watershed drains approximately 1,300 square miles of land, with 7.5% of the watershed in agriculture. Agricultural activities are concentrated in three productive areas: on the flood plain of the Pajaro River near the towns of Watsonville and Aromas ; in South Santa Clara Valley near Gilroy and San Martin ; and in the San Juan Valley near San Juan Bautista and Hollister . Production near the coast is dominated by cool-weather vegetables, berries, flowers, and apples. In the warmer inland areas—east of the Santa Cruz and Gabilan ranges—growers rotate crops of cool- and warm-weather vegetables, along with grapes, flowers, and stone fruits. Approximately 70 square miles in size, the Elkhorn Slough watershed drains northern Monterey County and a small portion of San Benito County. Approximately 24% of the watershed is in agriculture , with strawberries and cool-weather vegetables making up the majority of cultivated acreage .To assess the role of agricultural land use on phosphorus levels in waterways, we began sampling two creeks in October 2000 in the Elkhorn Slough watershed , and several waterways in the Pajaro River watershed, including Corralitos Creek, Watsonville Slough, the Pajaro River,procona valencia buckets and publicly accessible agricultural drainage ditches. In October 2002 we expanded the project to include all tributaries of the Pajaro River to determine the proportion of nutrients each water basin contributes to the river. We collected water samples every 2 weeks at approximately 60 sites throughout the watershed. Sites were selected to bracket agricultural activity and other land uses in order to compare concentrations upstream and downstream of potential nutrient sources. In addition, several locations were sampled more frequently to capture storm event variability and to measure water discharge for calculations of nutrient loads . For brevity we report here on several key sites that demonstrate spatial and temporal patterns we found to be characteristic of the entire watershed.Geographical patterns of dissolved phosphorus concentrations suggest that levels are influenced by land features as well as land use practices. Soil characteristics such as a shallow water table are associated with elevated stream SRP levels, particularly in agricultural areas. In the south Santa Clara Valley, SRP concentrations were low in all waterways with the exception of San Juan Creek. The San Juan drainage has a shallow, perched water table, and receives discharge from artificial tile drain systems, used in agricultural fields to remove water from the rooting zone of crop plants. In contrast, Llagas and Uvas Creeks, which do not receive tile drainage, had low SRP concentrations at all sites.

Median SRP concentrations increased slightly at sites downstream of agriculture , but exceeded the target level on fewer than 20% of visits . San Benito Creek and Miller’s Canal, which were both sampled near agricultural fields, also had low median SRP concentrations. The use of tile drainage systems may account for higher SRP levels in waterways with shallow water tables and agricultural land use, including Watsonville Slough and Corn Cob Canyon Creek. Tile drainage systems can increase phosphorus losses by increasing soil infiltration rate and reducing the amount of phosphorus that adheres to soil particles . During winter storms, tile drains may also act as conduits for particulate phosphorus, carrying eroded topsoil to waterways . Non-agricultural land uses, and occurrence of mineral types naturally high in SRP, may also contribute to elevated SRP concentrations in some areas. While nutrients were generally higher at locations downstream of agriculture, Corralitos Creek had elevated nutrients both upstream and downstream of agriculture. At the most upstream site , SRP concentrations often exceeded the target level of 0.12 mg/L while two other nutrients, nitrate and ammonium were very low. The elevated SRP levels are not likely from fertilizer or septic sources, which also tend to be high in nitrogen compounds, but may be due to the mineral composition of soils in this drainage and/or soil erosion. Comparisons of sites upstream and downstream of agriculture revealed higher downstream SRP concentrations in many waterways, providing evidence that agricultural land is a source of phosphorus in surface waters. In the Elkhorn Slough watershed, SRP progressively increased with the amount of cultivated acreage located upstream . The phosphorus content of the soils in the watershed may play a role in how phosphorus moves through this system, but this has not been looked at systematically. In Carneros Creek at Dunbarton Road, which is at the upstream edge of cultivated acreage, the median SRP concentration was 0.10 mg/L, and at San Miguel Canyon Road, downstream of several miles of farmland, the median concentration was 0.53 mg/L. However, in addition to row crops, land use along Carneros Creek is mixed with ranches and rural homes, and more intensive monitoring is necessary to partition nutrient inputs from these potential sources. In Corn Cob Canyon Creek, the median SRP concentration was 0.11 mg/L at Lewis Road, where the stream emerges from an underground culvert, and 2.2 mg/L at Hudson Landing, downstream of row crops. At the downstream locations in both Carneros and Corn Cob Canyon Creeks, SRP concentrations exceeded the 0.12 mg/L target level in 100% of biweekly samples. In Uvas and Llagas Creeks in the south Santa Clara Valley, SRP concentrations were generally below the target SRP concentration of 0.12 mg/L at all locations. However, water quality problems occurred more frequently downstream of agricultural land use , where a greater percentage of collected samples were over the target concentration . In the Pajaro River, elevated SRP concentrations occurred in the river’s upstream reaches at Chittenden Gap, due in large part to flow from San Juan Creek and associated ditches that drain irrigated fields in the San Juan Valley. In contrast to tributaries draining the south Santa Clara Valley, San Juan Creek had elevated SRP levels , and was a particularly significant source of nutrients to the Pajaro River during summer months, when flow from other creeks declined. In addition to San Juan Creek, several agricultural ditches in the south Santa Clara and San Juan Valley regions that flow intermittently may also contribute nutrients to the Pajaro River. We hope to address these issues in future research.In addition to agriculture, natural processes and urban runoff may also contribute phosphorus to waterways. Although no increase in phosphorus levels was detected at urban sampling locations on Llagas and Uvas Creeks , urban runoff from the city of Watsonville may contribute to elevated SRP levels in Watsonville Slough and the lower Pajaro River, particularly during the winter storm season. At Ohlone Road, our most upstream site in the slough, surface runoff from the city of Watsonville may also contribute to elevated SRP levels during winter storms. It is also worth noting that Watsonville Slough at Ohlone Road had a period of very high SRP concentrations in the late summer through fall of 2003; these may be associated with erosion from a development project that occurred adjacent to the sampling site.We detected seasonal changes in SRP concentrations in many waterways. One prominent seasonal pattern was an increase in SRP concentrations during the late summer in waterways that receive discharge from cultivated lands. This late summer increase occurred in San Juan Creek, in the Pajaro River at Chittenden Gap, and in Corn Cob Canyon Creek , and may be due to the combined effects of irrigation discharges and decreasing stream flows, which limit the capacity of waterways to dilute nutrient inputs.