Quantifying the influence of surface water–groundwater interaction on nutrient flux in a lowland karst catchment

Abstract

Abstract. Nutrient contamination of surface waters and groundwaters is an issue of growing importance as the risks associated with agricultural run-off escalate due to increasing demands on global food production. In this study, the influence of surface water-groundwater interaction on the nutrient flux in a lowland karst catchment was investigated with the aid of alkalinity sampling and a hydrological model. The objective of the study was to determine the impact of ephemeral karst lakes (turloughs) on the surface watergroundwater nutrient flux, and whether these lakes act as sources or sinks of nutrients within the groundwater flow system. Water samples were tested from a variety of rivers, turloughs, boreholes and springs at monthly intervals over 3 years. Alkalinity sampling was used to elucidate the contrasting hydrological functioning between different turloughs. Such disparate hydrological functioning was further investigated with the aid of a hydrological model which allowed for an estimate of allogenically and autogenically derived nutrient loading into the karst system. The model also allowed for an investigation of mixing within the turloughs, comparing observed behaviours with the hypothetical conservative behaviour allowed for by the model. Within the turloughs, recorded nutrient concentrations were found to reduce over the flooded period, even though the turloughs hydrological functioning (and the hydrological model) suggested this would not occur under conservative conditions. As such, it was determined that nutrient loss processes were occurring within the system. Denitrification during stable flooded periods (typically 3-4 months per year) was deemed to be the main process reducing nitrogen concentrations within the turloughs, whereas phosphorus loss is thought to occur mostly via sedimentation and subsequent soil deposition.The results from this study suggest that, in stable conditions, ephemeral lakes can impart considerable nutrient losses on a karst groundwater system.

A watershed approach to managing rainfed agriculture in the semiarid region of southern Mali: integrated research on water and land use

“…The few instances of increased production of cereal staples (millet and sorghum) were mainly due to land expansion rather than an increase in yield per ha (Traoré et al 2014). This calls for a new integrated systems approach to improve the current agricultural practices using broader units of analysis and intervention, such as landscape, catchment and watershed (Blackie and Robinson 2007;Peterson et al 2016;McCormack et al 2016).…”

An evaluation of semidistributed-pipe-network and distributed-finite-difference models to simulate karst systems

“…This model was improved in following years and used to compare different approaches to attempt to define the submarine groundwater discharge into Kinvara Bay (McCormack et al 2014 ), as well to gain insights into the nutrient processes in the turloughs and wider catchment using non-reactive solute tracer against field data (McCormack et al 2016 ). The main limitation of this semidistributed modelling approach based on urban drainage models that had become apparent, however, was the lack of spatial resolution possible with regard to the diffuse recharge component, as it is homogenised on a subcatchment basis and then simplified by the series of conceptual reservoirs.…”

Spatio-Temporal Dynamics of Riverine Nitrogen and Phosphorus at Different Catchment Scales in Huixian Karst Wetland, Southwest China

“…Analysis of spatio-temporal variations of nitrogen and phosphorus driven by hydrological conditions at different catchment scales help to improve the understanding of the coupled processes between water and nutrient cycling [25,26]. Thus, identifying the spatio-temporal variations of N and P transfer in karst water systems and revealing their influence factors have become one of the focus of international concern in karst ecology [27][28][29][30].…”