Citation:

Ghimire, S., R. Parmar, G. Mahadwar, AND R. Srinivasan. Water quality impacts of riparian buffer zones: A case study in the Albemarle-Pamlico river basin (USA) using HAWQS. International Society for Ecological Modelling Global Conference 2023 (ISEM 2023), Toronto, CANADA, May 02 - 06, 2023.

Impact/Purpose:

In this study, we summarize the riparian buffer zone (RBZ) design strategy and evaluate the RBZ water quality impacts as a component of watershed ecosystem services at watershed scale through sensitivity analyses of 135 simulation scenarios. The scenarios included the variation of six baseline RBZs (Grass, Urban, Two-zone Forest, Three-zone Forest, Wildlife, and Naturalized) in three 12-digit Hydrologic Unit Code (HUC12) watersheds (Back Creek, Sycamore Creek, and Greens Mill Run) within the Albemarle-Pamlico river basin (USA). Analyses revealed optimal RBZ designs. In terms of watershed ecosystem services, the optimal Urban RBZ in Sycamore Creek reduced Total Phosphorous, Total Nitrogen, Sediment, and Biochemical Oxygen Demand by 64%, 36%, 97%, and 99% respectively, in addition to raising Dissolved Oxygen by 13% with respect to the maximum values of no-RBZ.

Description:

A riparian buffer zone (RBZ) represents a designed or natural vegetated area for controlling non-point source contributions of sediments and nutrients to water bodies within a watershed. We summarize the RBZs’ design strategy and evaluate the RBZ water quality impacts as a component of watershed ecosystem services at watershed scale through sensitivity analyses. We designed 135 sensitivity simulation scenarios by varying the width of six baseline RBZs (Grass, Urban, Two-zone Forest, Three-zone Forest, Wildlife, and Naturalized) in three 12-digit Hydrologic Unit Code (HUC12) watersheds within the Albemarle-Pamlico river basin in the southeastern USA. We used the EPA/Texas A&M Hydrologic and Water Quality System (HAWQS) to simulate the RBZ scenarios tailored to the three HUC12 watersheds: Back Creek, Sycamore Creek, and Greens Mill Run. We evaluated impacts of RBZs on five instream water quality index (WQI) parameters: Dissolved Oxygen, Total Phosphorous, Total Nitrogen, Total Suspended Solids (as Sediment), and Biochemical Oxygen Demand concentrations (mg/L). We normalized the WQI parameter values with respect to maximum WQI parameter value for each RBZ scenario. The analysis revealed optimal design of RBZs for each watershed and showed the greatest improvements in WQI parameter values due to Urban RBZ of optimal width at 28.6 m. In terms of watershed ecosystem services, the optimal Urban RBZ in Sycamore Creek reduced Total Phosphorous, Total Nitrogen, Sediment, and Biochemical Oxygen Demand by 64%, 36%, 97%, and 99% respectively, in addition to raising Dissolved Oxygen by 13% with respect to the maximum values of no-RBZ. The improvements varied between watersheds. Future extreme climate conditions from drier to wetter and hotter to cooler also influenced the improvements. These preliminary findings will guide future RBZ analyses adapted to other watersheds and estimating the economic and environmental benefits to support decision making for improving and protecting water resources.

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