Current-use insecticides, phosphates and suspended solids in the Lourens River, Western Cape, during the first rainfall event of the wet season

Pesticide contamination resulting from agricultural runoff depends on the time period between application and rainfall. In Western Cape orchard areas, the last pesticide application of the growing season in summer takes place at the end of February. Pesticides, total phosphates and total suspended solids (TSS) were measured in the Lourens River at the beginning of April 1999 prior to the first rainfall of the rainy season and in the middle of April during high discharge following the first rainfall of 9.6 mm/d. Pre-runoff samples indicated only contamination with total endosulfan (α, β, sulphate) at levels up to 0.06 µg/l. Runoff during the first rainfall event resulted in an increase in the levels of endosulfan, chlorpyrifos and azinphos-methyl, to 0.16. WaterSA Vol.27(1) 2001: 65-7

Beaver Colony Density Trends on the Chequamegon-Nicolet National Forest, 1987 - 2013.

The North American beaver (Castor canadensis) is a managed species in the United States. In northern Wisconsin, as part of the state-wide beaver management program, the Chequamegon-Nicolet National Forest removes beavers from targeted trout streams on U.S. Forest Service lands. However, the success of this management program has not been evaluated. Targeted removals comprise only 3% of the annual beaver harvest, a level of effort that may not affect the beaver population. We used colony location data along Forest streams from 1987-2013 (Nicolet, northeast Wisconsin) and 1997-2013 (Chequamegon, northwest Wisconsin) to assess trends in beaver colony density on targeted trout streams compared to non-targeted streams. On the Chequamegon, colony density on non-targeted trout and non-trout streams did not change over time, while colony density on targeted trout streams declined and then stabilized. On the Nicolet, beaver colony density decreased on both non-targeted streams and targeted trout streams. However, colony density on targeted trout streams declined faster. The impact of targeted trapping was similar across the two sides of the Forest (60% reduction relative to non-targeted trout streams). Exploratory analyses of weather influences found that very dry conditions and severe winters were associated with transient reductions in beaver colony density on non-targeted streams on both sides of the Forest. Our findings may help land management agencies weigh more finely calibrated beaver control measures against continued large-scale removal programs

Improved stream food web function associated with stream simulation design culverts in northern Great Lakes streams

Typical goals of aquatic organism passage projects include providing adequate passage of aquatic organisms and rarely consider whether stream food web function is improved. We examined differences in habitat and food web responses (periphyton, organic matter, and invertebrates) in upstream, downstream, and culvert reaches at paired road-stream crossings in northern Wisconsin streams located within the Chequamegon-Nicolet National Forest. One culvert of each pair was constructed using the Stream Simulation Design (SSD) which mimics natural channel structure, while the other was left to fill on its own (non-SSD). Habitat characteristics within SSD crossings included shallower depths, faster velocities, and substrate dominated by cobble, pebble, and gravel, while silt dominated non-SSD crossings. Periphyton standing crop was greater in SSD crossings than non-SSD crossings. Fine benthic organic matter was significantly greater at non-SSD crossings than at all other reaches. Standing crops of coarse organic matter food resources (leaves/wood) and invertebrate abundances were significantly lower at non-SSD crossings compared to upstream and downstream reaches. Collector-gatherer chironomids dominated invertebrate communities at non-SSD crossings, while mayflies, stoneflies, and caddisflies dominated reaches at SSD sites. Food webs at SSD road-stream crossings more closely reflected reference reaches demonstrating that SSD can provide ecological functions beyond aquatic organism passage

Predicting runoff-induced pesticide input in agricultural sub-catchment surface waters : linking catchment variables and contamination

The original publication is available at http://www.sciencedirect.comAn urgent need exists for applicable methods to predict areas at risk of pesticide contamination within agricultural catchments. As such, an attempt was made to predict and validate contamination in nine separate sub-catchments of the Lourens River, South Africa, through use of a geographic information system (GIS)-based runoff model, which incorporates geographical catchment variables and physicochemical characteristics of applied pesticides. We compared the results of the prediction with measured contamination in water and suspended sediment samples collected during runoff conditions in tributaries discharging these sub-catchments. The most common insecticides applied and detected in the catchment over a 3-year sampling period were azinphos-methyl (AZP), chlorpyrifos (CPF) and endosulfan (END). AZP was predominantly found in water samples, while CPF and END were detected at higher levels in the suspended particle samples. We found positive (po0:002) correlations between the predicted average loss and the concentrations of the three insecticides both in water and suspended sediments (r between 0.87 and 0.94). Two sites in the sub-catchment were identified as posing the greatest risk to the Lourens River mainstream. It is assumed that lack of buffer strips, presence of erosion rills and high slopes are the main variables responsible for the high contamination at these sites. We conclude that this approach to predict runoff-related surface water contamination may serve as a powerfultool for risk assessment and management in South African orchard areas. r 2002 Elsevier Science Ltd. All rights reserved.Publishers' Versio

Location of the Chequamegon-Nicolet National Forest and the northern Wisconsin stream network.

<p>Streams surveyed during fall for active beaver colonies on the Chequamegon-Nicolet National Forest. Targeted streams are in magenta and non-targeted streams are in green. The grey background for the stream network is the topography of northern Wisconsin as represented by a hillshade model. Weather data were obtained from the indicated National Weather Service Cooperative Observer Program (COOP) weather stations.</p

Effort for aerial surveys of beaver colonies made October–November along four categories of streams in the Chequamegon-Nicolet National Forest, 1987–2013 (Nicolet side) and 1997–2013 (Chequamegon side).

<p>Targeted streams were subject to the beaver control program.</p

Beaver colony numbers/km by year for (a) trout streams without targeted beaver management and (b) trout streams with targeted beaver management for the Chequamegon-Nicolet National Forest.

<p>In panel (a), open circle = Nicolet trout streams, filled circle = Nicolet non-trout streams, open square = Chequamegon trout streams, filled square = Chequamegon non-trout streams. In panel (b), open circle = Nicolet side, triangle = Chequamegon side. Dotted lines are the predicted trends from generalized additive models (significant trends only).</p

Time trend and weather models for beaver colony density on streams where no targeted beaver management occurred on the Nicolet side of the Chequamegon-Nicolet National Forest, 1987–2013.

<p>Models listed are the minimum AIC model, competitive models (those models within 2 AC units of the minimum), and the trend model.</p

Weather models for beaver colony density on streams where no targeted beaver management occurred on the Chequamegon side of the Chequamegon-Nicolet National Forest, 1997–2013.

<p>Models listed are the minimum AIC model, competitive models (those models within 2 AC units of the 006Dinimum), and the 2007 drought model. The evidence ratio is the ratio of the Akaike weights for the minimum AIC model and an alternate model.</p