The groundwater contribution to surface water contamination in a region with intensive agricultural land use (Noord-Brabant, The Netherlands)

High‐frequency monitoring of catchment nutrient exports reveals highly variable storm event responses and dynamic source zone activation

“…This is supported by the observed link between HI and precipitation intensity and antecedent rainfall: thus, certain NO 3 -N sources (e.g., those in the surface or uppermost soil layers) are mobilized when particularly extreme streamflow conditions coincide with high levels of soil saturation. These conditions result in a greater proportion of precipitation converted to overland runoff or preferential flow through subsurface tile drainage networks [Rozemeijer and Broers, 2007;DarwicheCriado et al, 2015;van der Grift et al, 2016] with corresponding reductions in the influence of catchment subsurface storage on runoff and NO 3 -N export dynamics [Teuling et al, 2010]. In contrast, during drier periods, lower soil moisture conditions lead to greater infiltration potential, and thus, water and nutrient transport are dominated by subsurface flow pathways (Figure 7).…”

“…The most obvious sources of NO 3 -N are the current and former arable farmland areas (but also potentially also contaminated groundwater aquifers) in the upper catchment [Rozemeijer and Broers, 2007;Krause et al, 2009;Raymond et al, 2012]. As such, NO 3 -N hysteresis patterns are hypothesized to reflect hydroclimatological impacts on catchment flow pathways during storm events, resulting in hydrological connectivity and activation of nutrient source zones to the channel network that would not contribute to aquatic NO 3 -N export during base flow [Bowes et al, 2009].…”

Improving Load Estimates for NO3 and P in Surface Waters by Characterizing the Concentration Response to Rainfall Events

“…For example, several researchers reported peaks in P-concentrations in response to rainfall events (13,14). The NO 3 response to rainfall events depends on the hydrogeochemical properties of the catchment; some authors observed a lowering of concentrations (10,15,16), while others detected concentration peaks in response to events (17)(18)(19). The new understanding of shortscale variations in water quality has not yet been applied for improved methodologies for estimating loads from lowfrequency concentration data.…”

Macronutrient status of UK groundwater: Nitrogen, phosphorus and organic carbon

“…This has implications for drinking water utilities in the cost and reliability of treatment to meet the regulation quality. Elevated nitrate concentrations in groundwater may also impact on surface water where baseflow is significant and on groundwater dependent ecosystems (Rozemeijer and Broers, 2007;Sánchez-Pérez et al, 2003). The roles of nitrate and phosphate are interlinked in the surface water eutrophication process (Smolders et al, 2009).…”

“…Analysis for P species in groundwater has become more sophisticated, analogous to longer-established surface water practice, and a useful body of UK data for soluble reactive P in groundwater, for example, is developing. Rozemeijer and Broers (2007) showed that non-conservative contaminants, such as total P, migrate only slowly downwards through the aquifer and thus show large contributions to surface water during rapid flow events. With the increasing frequency of extreme climatic events in the UK, it would be reasonable to assume that higher loadings of mobile P will be discharged to groundwater receptors in the future.…”