Monitoring stream sediment loads in response to agriculture in Prince Edward Island, Canada

Abstract

Increased agricultural land use leads to accelerated erosion and deposition of fine sediment in surface water. Monitoring of suspended sediment yields has proven challenging due to the spatial and temporal variability of sediment loading. Reliable sediment yield calculations depend on accurate monitoring of these highly episodic sediment loading events. This study aims to quantify precipitation-induced loading of suspended sediments on Prince Edward Island, Canada. Turbidity is considered to be a reasonably accurate proxy for suspended sediment data. In this study, turbidity was used to monitor suspended sediment concentration (SSC) and was measured for 2 years (December 2012-2014) in three subwatersheds with varying degrees of agricultural land use ranging from 10 to 69 %. Comparison of three turbidity meter calibration methods, two using suspended streambed sediment and one using automated sampling during rainfall events, revealed that the use of SSC samples constructed from streambed sediment was not an accurate replacement for water column sampling during rainfall events for calibration. Different particle size distributions in the three rivers produced significant impacts on the calibration methods demonstrating the need for river-specific calibration. Rainfall-induced sediment loading was significantly greater in the most agriculturally impacted site only when the load per rainfall event was corrected for runoff volume (total flow minus baseflow), flow increase intensity (the slope between the start of a runoff event and the peak of the hydrograph), and season. Monitoring turbidity, in combination with sediment modeling, may offer the best option for management purposes.

Factors Influencing Brook Trout (Salvelinus frontinalis) Egg Survival and Development in Streams Influenced by Agriculture

“…Wheatley River, located in the central portion of the island, had the highest amount of agricultural activity in the watershed, while the Souris and Cross Rivers, located in the eastern portion of the island, had intermediate and lowest levels of agriculture (Table 1 and Figure 1). Detailed characterization of the sediment load in these watersheds is provided in Alberto et al (2016). Each river has a population of brook trout.…”

“…Salmonid spawning gravel is considered to be of poor quality if fine content exceeds 15% (O'Connor and Andrew, 1998). Intensive agriculture has been shown to be an important source of increased sediment load (Alberto et al, 2016).…”

Impacts of hypoxia on estuarine macroinvertebrate assemblages across a regional nutrient gradient

“…Unlike Z. marina, which has strict substrate requirements, Ulva grows ephemerally, in nutrient-enriched systems, and is therefore not limited by grain size (Webster et al 1998;Gamito et al 2012). In this study, average substrate particle size (D50) had a greater range at Ulva sites (22-235 μm) compared with Z. marina sites (36-89 μm), presumably due to some combination of higher levels of fine sediment input from agriculture (Alberto et al 2016) and differences in local lithology (van der Poll 1983) and hydrology. Furthermore, Ulva-dominated sites experience greater dissolved oxygen variability than Z. marinadominated sites (Coffin et al submitted), which may limit the number of taxa capable of inhabiting them.…”

Response of the Meltwater Erosion to Runoff Energy Consumption on Loessal Slopes

“…The soil erosion rate for the three slopes, ranging from largest to smallest, were: frozen > shallow-thawed > unfrozen (Figure 3 and Table 1). Previously frozen soil is highly susceptible to riling even from low intensity rainfall and runoff [29], which could occur during much of the Prince Edward Island cool period [62]. Under the same flow conditions, the thawed soil rill transports more sediment than the unfrozen soil rill [6,60].…”