Relation between Irrigation Method, Sediment Yields, and Losses of Pesticides and Nitrogen

Abstract

Yields of suspended sediment from watersheds in the Quincy and Pasco Basins of Washington State have been reduced by the use of sprinkler irrigation on cropland previously in furrow irrigation. Mean daily yields of suspended sediment from nine watersheds sampled during April and May 1994 ranged from 0.4 kg/ha of irrigated cropland in a watershed with no furrow irrigation to 19 kg/ha in a watershed where 58% of irrigated cropland was in furrow irrigation. About 67% of the variation in the yields can be attributed to irrigation method. Temporal trends also indicated that use of sprinkler irrigation reduced sediment yields. Mean daily yields of suspended solids from one of the watersheds decreased from 0.3 kg/ha in 1975 to <0.2 kg/ha in 1988, corresponding with a decrease from about 65% to <50% in the use of furrow irrigation. Sampling in two watersheds suggests that the use of sprinkler irrigation reduces runoff losses of pesticides and N. For 10 of 13 pesticides and N, runoff losses from a watershed with mostly furrow irrigation exceeded runoff losses from a watershed with mostly sprinkler irrigation.

Pesticides in surface water of the Yakima River basin, Washington, 1999–2000 — Their occurrence and an assessment of factors affecting concentrations and loads

“…Instead, pesticide loss can be considered as an indicator of pesticide mobility or usage practices that affect the movement of a pesticide to surface water. Pesticide losses ranged from less than 0.01 to 1.5 percent of pesticides applied (table 13) and are comparable to those observed (0.01 to 2.2 percent) in irrigated agricultural basins in the central Columbia Plateau of Washington State (Ebbert and Kim, 1998).…”

“…Loads for this time period were obtained by summing daily loads, which were computed as the product of a daily concentration, either measured or interpolated, and the daily mean water discharge. Although the use of linear interpolation to estimate pesticide concentrations on days when no samples were collected is relatively simple compared with some other methods, it has been used when samples are closely spaced in time (Larson and others, 1995), and it was used for fixed-site data collected from rivers and irrigation wasteways in the central Columbia Plateau of Washington State (Ebbert and Kim, 1998).…”

On the relative importance of the remote and local wind effects to the subtidal variability in a coastal plain estuary

“…Yields of suspended sediment from watersheds in the Quincy and Pasco Basins of Washington state have been reduced by the use of sprinkler irrigation on cropland previously in furrow irrigation. Mean daily yields of suspended solids from one of the watersheds decreased, which corresponded with a decrease in the use of furrow irrigation (Ebbert and Kim, 1998). The association of triorganotin compounds (TOTs) with dissolved Aldrich and Suwannee River humic acids was investigated as a function of pH and sodium perchlorate concentration.…”

Factors Affecting the Occurrence and Distribution of Pesticides in the Yakima River Basin, Washington, 2000

“…Their result was corroborated by laboratory analyses that demonstrated no analytical difference between the concentration of atrazine in a centrifuged sample and the concentration of total atrazine in unfiltered, uncentrifuged water. For the purposes of this report, atrazine is considered to have a low K oc value (around 100 mL/ g); however, Ebbert and Kim (1998) dissolved fraction for a hypothetical pesticide with a moderately high K oc value (20,000 mL/g) and determined that it also should occur primarily in the dissolved phase (97 percent). Rinella and others (1999) calculated the fraction of total pesticide expected to occur in the dissolved phase for a range of K oc values (5,000-4,000,000 mL/g) and suspendedsediment concentrations (0-1000 mg/L) of known organic-carbon content in Yakima River Basin waterways.…”