Finite Element Simulation of Total Nitrogen Transport in Riparian Buffer in an Agricultural Watershed

Abstract

Riparian buffers can influence water quality in downstream lakes or rivers by buffering non-point source pollution in upstream agricultural fields. With increasing nitrogen (N) pollution in small agricultural watersheds, a major function of riparian buffers is to retain N in the soil. A series of field experiments were conducted to monitor pollutant transport in riparian buffers of small watersheds, while numerical model-based analysis is scarce. In this study, we set up a field experiment to monitor the retention rates of total N in different widths of buffer strips and used a finite element model (HYDRUS 2D/3D) to simulate the total N transport in the riparian buffer of an agricultural non-point source polluted area in the Liaohe River basin. The field experiment retention rates for total N were 19.4%, 26.6%, 29.5%, and 42.9% in 1,3,4, and 6m-wide buffer strips, respectively. Throughout the simulation period, the concentration of total N of the 1mwide buffer strip reached a maximum of 1.27 mg/cm 3 at 30 min, decreasing before leveling off. The concentration of total N about the 3mwide buffer strip consistently increased, with a maximum of 1.05 mg/cm 3 observed at 60 min. Under rainfall infiltration, the buffer strips of different widths showed a retention effect on total N transport, and the optimum effect was simulated in the 6mwide buffer strip. A comparison between measured and simulated data revealed that finite element simulation could simulate N transport in the soil of riparian buffer strips.

Assessment of Long-Term Watershed Management on Reservoir Phosphorus Concentrations and Export Fluxes

“…Excessive P concentrations and loads in reservoirs are largely attributed to the overuse of anthropogenic P (e.g., industrial and domestic sewage, P fertilizer, livestock excrement) within the watershed. Thus, improvement of reservoir water quality depends on pollution load reductions by means of integrated watershed pollution control measures including source management [ 15 ], process control [ 16 ], and end-of-pipe treatment [ 17 ]. It has been generally recognized that source management is a fundamental strategy for sustainable watershed P management and integrated pollution control [ 15 ].…”

Effectiveness of Riparian Vegetated Filter Strips in Removing Agricultural Nonpoint Source Pollutants in Agricultural Runoff from the Liao River Area, China

“…Many factors affect the efficacy of RVFS in removing contaminants, including vegetation type, RVFS width, slope, soil, climate, topography, and hydrological processes, which influence their efficiency in trapping contaminants [20]. The 1-6 m wide riparian vegetated buffer strips could retain total nitrogen in the range of 19.4%-42.9% [21]. Alukwe and Dillaha [22] reported phosphorous trapping efficiency of 73 % for a 4.6-m width vegetated filter strips (VFS) with a slope of 11%, whereas with a 16% slope, the trapping efficiency was 49% for the same width VFS.…”

Vegetated Buffer Zone Restoration Planning in Small Urban Watersheds

“…Typically, widths of 5-300 m are required to filter 10-95% sediments and nutrients [19][20][21], and scholars offer advised width through investigations, experience, or mathematical models [22,23]. Complicated models like REMM (Riparian Ecosystem Management Model) [24,25], CREAMS (Chemical, Runoff and Erosion from Agricultural Management System Model) [26], and VFSMOD (Vegetative Filter Strips Model) [27] that are based on the whole physical process of sediment and pollutant deposition and migration can simulate the minimum width for specific removal efficiency of different riparian zones [28]. Some multi-functional hydrological models like SWAT also integrate a buffer width module [29].…”