Changes in Nutrient Emissions, Fluxes and Retention in a North-Eastern European Lowland Drainage Basin

Abstract

Despite dramatic reductions in the 1990s of N and P emissions in the drainage basin, Lake Peipsi/Chudskoe (Estonia/Russia) is still suffering from algal blooms, probably caused by low N:P ratios of the lake water. To quantify the sources and changes of N and P inputs to the lake as a result of economic changes, we modelled emissions, transfer and in-stream retention using a GIS model. The model was calibrated using river monitoring data from the 1985-1989 period, and used to simulate emissions and loads for five future scenarios for 2015-2019. During the 1985-1999 period, diffuse P emissions decreased relatively more than N diffuse emissions, but this was not reflected in the loads to the lake. P loads decreased relatively less than N loads, which caused a decrease in the N:P ratio of the rivers. About 30-45% of diffuse N emissions and only 3-10% of diffuse P emissions reaches the river network. In-stream retention reduces N and P loads to the lake by about 62% and 72%, respectively. Point sources contribute negligibly to the N load to the lake, but form about one-third of the P load. A target/fast development scenario is the most likely scenario for the 2015-2019 period, resulting in higher nutrient loads than in recent years. We conclude that effective load reductions can be achieved by focussing on diffuse N and P emissions close (< 50 km2) to the lake and by upgrading P removal capacity in wastewater treatment plants of towns.

Nitrogen Source Apportionment for the Catchment, Estuary, and Adjacent Coastal Waters of the River Scheldt

“…For the PCRaster grid model, we closely followed the model structure of De Wit (2001) and Mourad et al (2006), which estimates for each grid point the nitrogen flux due to diffuse and point sources into soil, subsoil, groundwater, and surface water. This is done using a temporal resolution of 1 yr and a spatial resolution of 1 km².…”

“…PCRaster (http://www.PCRaster.nl) has been used satisfactorily to model water and nutrient fluxes through a drainage network for several river basins (De Wit 2001, Pieterse et al 2003, Mourad et al 2006. A priori requirements for the model suite were: (1) to provide sufficient spatial resolution and representation of different types of land use included in the Scheldt basin; (2) to cover diffuse and point nutrient sources; (3) to include surface and groundwater flow; (4) to allow flexibility in the inclusion of different nutrient abatement measures; (5) to include economic land-use decisions by farmers, who can go bankrupt; (6) to include scenarios of climate change and possible future societal development such as those in the IPCC Special Report on Emissions Scenarios (SRES; Berkhout and Hertin 2000, Lorenzoni et al 2000, Busch 2006, Van den Hurk et al 2006, Verburg et al 2006.…”

Pool of mobile and immobile phosphorus in sediments of the large, shallow Lake Peipsi over the last 100 years

“…While the external loading of Lake Peipsi sensu stricto (s.s.) has been extensively studied (Mourad et al 2006;Loigu et al 2008;Buhvestova et al 2011), comparatively few studies exist on the phosphorus release from sediment. The P flux at the sedimentwater interface is far from negligible and should be taken into account in lake management activities of L. Peipsi s.s. (Punning and Kapanen 2009).…”

Spatio‐temporal patterns of nutrient concentrations and export in a north‐eastern European lowland catchment

“…For DIN we took a value of k equal to 1Ð75 day 1 (at 20°C) and for DRP a value of k equal to 1Ð25 day 1 as reported by Van der Perk (2006). These rate constants were measured in northern European river systems, which are comparable to the Ahja River catchment with respect to geology, geomorphology, and climate (Mourad et al, 2006). The first-order rate constant for DIN removal was assumed to be temperature dependent according to (Thomann and Mueller, 1987): where k T is the temperature corrected rate constant (day 1 ), Â is the temperature coefficient ( ), which is usually set to 1Ð08, and T is the water temperature (°C).…”

“…Agriculture has been decreasing since the beginning of the 1990s, when Estonia returned to free market economy after nearly 50 years of Soviet economy. This chaotic transition resulted in the neglect of many fields, deterioration of subsurface drainage systems, and a decrease in cropland (Mander and Palang, 1994;Unwin, 1997;Peterson and Aunap, 1998), accompanied by a significant decrease in nutrient emissions and a subsequent improvement of water quality (Loigu and Leisk, 1996;Mander et al, 2000a;Stålnacke et al, 2002;Iital et al, 2005;Mourad et al, 2005;Mourad et al, 2006). The current, scattered, agricultural activities result in a highly variable fertilizer input on the different agricultural fields.…”