Seasonal Sediment and Nutrient Transport Patterns

Abstract

It is essential to understand sediment and nutrient sources and their spatial and temporal patterns to design effective mitigation strategies. However, long-term data sets to determine sediment and nutrient loadings are scarce and expensive to collect. The goal of this study was to determine seasonal patterns of suspended sediment (SS), total N (TN), and total P (TP) concentrations and loadings for three USGS gauge sites located at the Fort Cobb Reservoir Experimental watershed (FCREW) located in southwestern Oklahoma. Measured instantaneous discharge, SS, TN, and TP concentration data were used to develop lognormal water quality-discharge relationships. The water quality-discharge relationships were used to generate estimated seasonal concentrations and loads based on hourly or 30-min interval discharge. The estimated concentrations and loads were used to determine seasonal patterns for SS, TN, and TP relative to the respective state water quality criteria. Decreasing and increasing monotonic trends were observed for the seasonal time series loads for all three sites, but they were insignificant based on the Spearman test (α = 0.05). The largest loads were estimated during the wet springs and summers. The study SS, TN, and TP target concentrations were exceeded in one season or another. The study results showed that the priority locations to implement the TN and TP conservation practices were the Lake Creek and Willow Creek subwatersheds during the winter and spring seasons. Common practices to mitigate nutrients and suspended sediments include nutrient management, no-till, conversion of cultivated land to pasture, riparian buffers, and animal exclusion.

Long-Term Environmental Research: The Upper Washita River Experimental Watersheds, Oklahoma, USA

“…Moriasi et al (2014a) present data on seasonal and annual loads of nutrients and sediments to the Fort Cobb Reservoir as affected by high‐flow events and seasonality, with mitigation options to address total maximum daily load. Additionally, they analyze streamflow–rainfall cross‐correlations at different temporal scales to determine the impact of temporal rainfall resolution on streamflow–rainfall relationships, the effect of drainage area on peak flow and time to peak, and the corresponding implications on sediment and nutrient loadings to water bodies.…”

SWAT‐LUT: A Desktop Graphical User Interface for Updating Land Use in SWAT

“…The daily streamflow data were downloaded from the USGS web site (http://waterdata.usgs.gov/ok/nwis/rt). Water quality data collected by the USGS at each stream gage site for the 2005–2014 period were used to develop rating curves (Moriasi, Guzman, et al ), which were used to generate daily sediment, total nitrogen and total phosphorus loads. The baseline SWAT project was built using ArcSWAT (Winchell et al ), delineating the watershed into 79 subbasins, whereas the number of HRUs varied depending on the land use maps used.…”

Probabilistic approach to modeling under changing scenarios

“…The baseline model (scenario 1) was defined according to the land use characteristics presented in Moriasi et al (2014a). The main land uses in the Lake Creek watershed were winter wheat crops and pasture.…”

“…This may be achieved through long-term monitoring and research (Starks, et al, 2014;Tomer & Locke, 2011) that can also support the evaluation of conservation practices and provide data for model development. However, long-term datasets with high spatio-temporal resolution are scarce and expensive to collect (Moriasi et al, 2014a). In addition, the complexity linked to agro-production systems does not allow social and cost-effective experimentation at large scales (Gassman, et al, 2007).…”