Non-linear response of a mixed land use watershed to nitrogen loading

Effects of watershed and riparian zone characteristics on nutrient concentrations in the River Scheldt Basin

“…The importance of point sources for water quality depends on the extent of industrial activity and urban land with respect to the basin area under agriculture and forest and the level and efficiency of pre-discharge treatment processes (Ometo et al, 2000). Diffuse sources are more difficult to monitor because nutrients follow a variety of pathways depending on the hydrological routing between overland, subsurface and base flow (Haycock et al, 1993;Nikolaidis et al, 1998;Dzikiewicz, 2000). Different flow components dominate N and P concentrations and export.…”

Impacts of a Manure Composting Program on Stream Water Quality

“…First, although direct P inputs to the land were decreased with implementation of the manure composting program, instream improvements generally lag improvements on the land (Clausen et al, 1992;Meals, 1992Meals, , 1996Nikolaidis et al, 1998). Based on field monitoring data and mathematical modeling, Nikolaidis et al (1998) reported less than 1.5% reduction in N export after three years following a 100% reduction in fertilizer and manure input to agricultural land in north-central Connecticut. They attributed the lack of immediate response in water quality to the non-linear response of watersheds to implementation of land management practices.…”

“…They attributed the lack of immediate response in water quality to the non-linear response of watersheds to implementation of land management practices. Nikolaidis et al (1998) offer two reasons for non-linearity in watershed response: (1) inherent watershed characteristics and hydrochemical processes that delay nutrient loading in response to rainfall runoff, and (2) land use patterns and position of contributing sources within a watershed. Phosphorus fits this non-linear response in that residual SRP can be released from the land and from the resuspension of sediments at elevated flows within the stream system (Brannan et al, 2000).…”

“…On the watershed scale, it is often difficult to control these confounding factors, and changes in water quality generally occur more gradually. Changes in water quality associated with nonpoint-source contributions often lag changes in land management because of residual impacts from past management practices (Clausen et al, 1992;Meals, 1992Meals, , 1996Nikolaidis et al, 1998). The length of this time lag can vary greatly, particularly with regard to P, based on whether the soil itself is acting as a sink or source of P (Sharpley, 1995;Sharpley and Rekolainen, 1997).…”

Urbanization, Water Quality Degradation and Irrigation for Agriculture in Nhue River Basin of Vietnam

“…Studying the pathway and pollution of phosphorus at a watershed in the western USA, McDowell and Sharpley (2003) concluded that they need to apply integrated measures on management of manures, agricultural farming and developing natural filters and strengthen production management to mitigate environmental pollution. Using Nutrient Transport and Transformation (NTT) to simulate the transpotation of nitrogen at Muddy Brook watershed in north-west of Connecticut, USA, Nikolaidis et al (1998) based on the research results to give a management guideline to choose suitable managements to improve water quality in the river and tream network. Modelling is a good trend to assess the current environment, validate the results of management and planning measures in the watershed, for example, mass of pollutants from Glumso lake, Denmark were also simulated (Zhang and Jorgensen, 2005) using Pamolare model; use of GIS and Agricultural Non-Point Pollution Source (AGNPS) to assess the water quality due to changing of land use (He, 2003).…”