Examining water quality effects of riparian wetland loss and restoration scenarios in a southern Ontario watershed / Wanhong Yang, Yongbo Liu, Chunping Ou, and Shane Gabor.

Includes bibliographical references (pages 33-34).

Wetland conservation has two important tasks: The first is to halt wetland loss and the second is to
conduct wetland restoration. In order to facilitate these tasks, it is important to understand the environmental
degradation from wetland loss and the environmental benefits from wetland restoration. The
purpose of the study is to develop SWAT based wetland modelling to examine water quality effects of
riparian wetland loss and restoration scenarios in the 323-km2 Black River watershed in southern
Ontario, Canada. The SWAT based wetland modelling was set up, calibrated and validated to fit into
watershed conditions. The modelling was then applied to evaluate various scenarios of wetland loss from
existing 7590 ha of riparian wetlands (baseline scenario) to 100% loss, and wetland restoration up to the
year 1800 condition with 11,237 ha of riparian wetlands (100% restoration). The modelling was further
applied to examine 100% riparian wetland loss and restoration in three subareas of the watershed to
understand spatial pattern of water quality effects. Modelling results show that in comparing to baseline
condition, the sediment, total nitrogen (TN), and total phosphorus (TP) loadings increase by 251.0%,
260.5%, and 890.9% respectively for 100% riparian wetland loss, and decrease by 34.5%, 28.3%, and 37.0%
respectively for 100% riparian wetland restoration. Modelling results also show that as riparian wetland
loss increases, the corresponding environmental degradation worsens at accelerated rates. In contrast, as
riparian wetland restoration increases, the environmental benefits improve but at decelerated rates.
Particularly, the water quality effects of riparian wetland loss or restoration show considerable spatial
variations. The watershed wetland modelling contributes to inform decisions on riparian wetland conservation
or restoration at different rates. The results further demonstrate the importance of targeting
priority areas for stopping riparian wetland loss and initiating riparian wetland restoration based on
scientific understanding of watershed wetland effects.