Phosphorus Loss from a Mixed Land Use Catchment in Northwest Spain

Abstract

This work examined P loss from a mixed land use catchment in northwest Spain and how it was related to hydrological factors. A stream draining a mixed land use catchment of 16 km in northwest Spain was monitored for 5 yr. Water samples were taken more frequently with increased stream flows. A total of 132 runoff events of different magnitudes were analyzed in this study. Mean annual P loss from the catchment was 11.5 kg km, about 68% being transported during runoff events, which only contributed to 29% of the flow. The contribution of runoff events to particulate P and dissolved P losses was 76 and 46% of total losses during the study period, respectively. A high interannual variability in P loss was observed, the differences being related to rainfall amount and distribution. At a seasonal scale, the highest P loads and concentrations were observed during rainy seasons; the lowest P loads occurred in summer because they occurred with stream flow. Particulate P accounted for the greatest proportion (74%) of transported P. There was a high variability in P transported between runoff events, with maximum discharge and discharge increase being the most important variables explaining total P concentration in these events through their effect on suspended sediment concentration.

Podejście do jakości wody w zlewni osadzonej w krajobrazie rolno-leśnym nieznacznie zdegradowanym przez działalność rolniczo-hodowlaną

“…In relation to P, the mean annual flow-weighted concentrations were 31.86, 22.78, and 9.07 µg L -1 for TP, PP, and DP, respectively, showing a strong range of variation over the study period, especially particulate fraction (2.96-433.17 µg L -1 ), in part reflecting the high variability in SS levels (table 1). The maximum TP and PP values occurred at the same time as the maximum SS concentration (511 mg L -1 ) coinciding with an erosive rainfall event, which activated sediment sources close to the stream (rills and ephemeral gullies developed in an agricultural field next to the stream) producing a high SS concentration [28,34]. Therefore, the highest TP and PP concentrations can be attributed to the rapid mobilization and arrival of the sediment adsorbed P to the stream.…”

Identifying seasonal patterns of phosphorus storm dynamics with dynamic time warping

“…The concentration of certain elements, such as phosphorus (P), can increase by one to several orders of magnitude during storms [ Heathwaite and Dils , ; Sharpley et al ., ]. Combined with the increase in discharge (Q), P export rates during storm events surpass those in base flow conditions; so, storm events can represent a large part of the annual P load in rural watersheds [ Gburek and Sharpley , ; Pionke et al ., ; Melland et al ., ; Rodriguez‐Blanco et al ., , ]. Another reason that scientists focus on storm events is that dynamics of P concentrations during storms can be analyzed to infer spatial origins of sources and dominant transport pathways.…”