Coupling hysteresis analysis with sediment and hydrological connectivity in three agricultural catchments in Navarre, Spain

Abstract

Purpose: Rain storm events mobilise large proportions of fine sediments in catchment systems. 28 Sediment from agricultural catchments are often adsorbed by nutrients, heavy metals and other 29 (in)organic pollutants that may impact downstream environments. To mitigate erosion, 30 sediment transport and associated pollutant transport it is crucial to know the origin of the 31 sediment that is found in the drainage system and, therefore, it is important to understand 32 catchment sediment dynamics throughout the continuity of runoff events. 33 Materials and methods: To assess the impact of the state of a catchment on the transport of 34 fine suspended sediment to catchment outlets an algorithm has been developed which classifies 35 rain storm events into simple (clockwise, counterclockwise) and compound (figure-of-eight; 36 complex) events. This algorithm is the first tool that uses all available discharge and suspended 37 sediment data and analyses these data automatically. A total of 797 runoff events from three 38 experimental watersheds in Navarre (Spain) were analysed with the help of long-term, high 39 resolution discharge and sediment data that was collected between 2000-2014. 40 Results and discussion: Morphological complexity and in-stream vegetation structures acted 41 as disconnecting landscape features which caused storage of sediment along the transport 42 cascade. The occurrence of sediment storage along transport paths was therefore responsible 43 for clockwise hysteresis due to the availability of in-stream sediment which could cause the 44 "first flush" affect. Conversely, the catchment with steeper channel gradients and a lower 45 stream density showed much more counterclockwise hysteresis due to better downstream and 46 lateral surface hydrological connectivity. In this research hydrological connectivity is defines 47 as the actual and potential transfer paths in a catchment. The classification of event SSC-Q 48 hysteresis provided a seasonal benchmark value to which catchment managers can compare 49 runoff events in order to understand the origin and locations of suspended sediment in the 50 3 catchment. 51 Conclusions: A new algorithm uses all available discharge and suspended sediment data to 52 assess catchment sediment dynamics. From these analysis, the catchment connectivity can be 53 assessed which is useful to develop catchment land management.

Distributive Characteristics of Riverine Nutrients in the Mun River, Northeast Thailand: Implications for Anthropogenic Inputs

“…In reality, the industrial inputs were mostly from sewage, which means that the pollutant can directly discharge into the rivers, while the pollutants from agricultural activities, such as the application of fertilizers, firstly enter the soil; undergo complex physical, chemical, and biologic processes; and then transfer into the rivers by soil erosion or the groundwater. Considering the occurrence, quantities, and connectivity of overland flow [51,52], the majority of the influence factors were similar between the wet and dry seasons. The difference in rainfall should be the dominant factor of the flow, and the high precipitation in the wet season increased the overland flow connectivity [53].…”

Impact Assessments of Rainfall–Runoff Characteristics Response Based on Land Use Change via Hydrological Simulation

“…The hydrologic response to land use change reveals that land use change alters elements such as evapotranspiration [8,9], runoff depth [10,11], mean annual runoff [12][13][14], snowmelt [1,15], soil erosion [16,17] and the groundwater quality [18] to affect overall basin hydrology. It is well documented that land use change therefore can have a significant effect on river basin hydrology, which is mainly reflected on the change of the flood volume [1,9], peak flow discharge [10,13], flood frequency [19] and peak flow rate [20].…”

Comparison of Acoustic to Optical Backscatter Continuous Measurements of Suspended Sediment Concentrations and Their Characterization in an Agriculturally Impacted River

“…The counter-clockwise hysteresis may be the result of late arrival of sediment at the point of measurement and the timing of the rainfall events or spatial location could explain waves of higher SSC arriving after the flow had started to decline [53][54][55]. The hysteresis loop pattern may be linked to the characteristics of the source sediment as well as to the frequency and intensity of precipitation [24,56,57].…”

“…Investigations over recent decades show an increasing interest in links between the drivers of suspended sediment transport in rivers and the uncertainties related to their spatial and temporal variability [21][22][23]. Hydro-climatic factors, in interaction with catchment characteristics, have been identified as the dominant drivers for suspended sediment loading over many time scales [24][25][26]. However, sediment budget variation was found to be strongly dependent on local conditions and there is still need of a better understanding of the functional relationships between variables that most affect sediment dynamics.…”