Movement of Nitrogen through an Agricultural Riparian Zone: 2. Distributed Modeling

Abstract

The Nutrient Transport and Transformation model (NTT) is a generalized fate, speciation and transport model capable of simulating the movement of nutrients in the environment. The hydrologie model is an energy-driven, distributed parameter model that couples surface and ground waters. The vertical discretization consists of overland flow, perched saturated layer, root zone, percolation zone, and groundwater. The chemical model is based on the mass balances of nitrate, ammonium ion, organic nitrogen, humus material, organic phosphorus, phosphate, litter and biomass in the unsaturated zone and the groundwater. Geochemical processes affecting the nitrogen species mass balance that are included are nitrification, denitrification, plant uptake, mineralization, litter partition, humidification, decomposition, and biomass growth (uptake) and respiration. The NTT model was used to simulate the fate, transport and speciation of nitrogen through a corn riparian zone using data collected during the summer months of 1992. The NTT model was shown to be capable of simulating the hydrologic and biogeochemical processes occurring in riparian zones. The root mean square error between the simulated and observed nitrate concentration is 1 mg/l. The model can be used in the design of riparian buffers for nonpoint source pollution control.

MODELING OF NONPOINT SOURCE POLLUTION OF NITROGEN AT THE WATERSHED SCALE1

“…The agricultural land use export coefficient was estimated to be 5.7 kg N/ha-yr. Denitrification in the unsaturated zone of the agricultural land use accounted for 10 percent of the nitrate loading. These results are consistent with the results reported by Nikolaidis et al (1993b). Martin (1996) measured the ground water nitrate concentration 5 m and 2.5 m away from the stream in the same agricultural land in the Muddy Brook Watershed and found that the nitrate concentration drops from 8 to 10 mg NIL at the 5 m wells to 2 to 3 mg N/I at the 2.5 m wells.…”

The Characteristics of Riparian Buffer Studies

“…Karr (1991) called for "ecologically sound tools" with a broad base of input from many disciplines to protect water quality. Carpenter et al (1998), Clausen et al (1993), Cooper (1993), and Nikolaidis et al (1993) all focused on water quality by modeling the behavior of non-point source pollutants (NPSP) from agricultural sources within a riparian buffer. Hanson et al (1994) examined Nitrogen and Carbon contents within riparian buffers.…”

“…With an increase in enlightenment of how well the riparian buffers control and reduce NPSP (Addy et al, 1999;Gilliam, 1994;Lowrance et al, 1997;Martin et al, 1999;Nikolaidis et al, 1993), issues of buffer restoration Large et al, 1993) and performance (Blackwell et al, 1999) became eminent.…”

Nonpoint sources

“…The Nutrient Transport and Transformation (NTT) model was shown to be capable of simulating the transport and speciation of nitrogen in ground and surface water moving through a com riparian zone (Nikolaidis et al. 1993).…”