Hydrologic Monitoring at Van Vleck Mitigation Bank
During a recent sunny day I had the privilege of spending time out of the office and in the field helping our senior ecologist complete some hydrologic monitoring at our Van Vleck Mitigation Bank. Although I would never complain about getting to spend the day outside in the beautiful rolling grassland I wasn’t quite sure why the monitoring was so important. “I’m no biologist” I joked and asked if he could explain the reasoning behind the hydrologic monitoring.
“Well,” he said as he recorded another pool depth on his sheet, “It’s simple really…” and he began to explain.
“As you know, the landscape here at Van Vleck Mitigation Bank is an annual grassland supporting wetlands, the majority of which are vernal pools and vernal swales. After we completed construction of the vernal pools within the Bank back in September, 2009 we immediately began to monitor the hydrology of both existing and created vernal features in early October of that year.”
The goal of this monitoring was to:
1) Help track habitat progression toward performance standards to ensure constructed wetlands are ecologically functional (i.e. providing species habitat and improving water quality in the area); and
2) Help evaluate and guide site stewardship activities, allowing for adaptive management when needed.
“Monitoring is critical to the successful establishment of vernal pools on the Bank and takes place over a five-year period following construction, ensuring the viability of created pools and the continued ecological stability (e.g. dominance of locally native vernal pool species) in existing pools.”
“We do this by systematically sampling a subset of the constructed pools and comparing their function to existing vernal pools. Approximately 20% of the roughly 248 constructed pools are monitored during each monitoring year. Sample pools were selected upon completion of construction, and were chosen to provide an accurate representation of all constructed pools on the Bank, based on characteristics such as: depth, acreage, and position within the landscape. Each of these selected pools was identified prior to the initiation of year one monitoring, and these sample locations remain unchanged throughout the duration of the five year Interim Monitoring Period.”
“Constructed pools are compared to a minimum of ten percent (10%) of vernal pools that existed onsite prior to construction, totaling 50 in number, which were selected as reference pools prior to the start of post-construction monitoring. Reference pools were selected based upon the same characteristics as created pools (i.e. depth, acreage, and position within the landscape) and were selected to produce an accurate representation of the characteristics present across the entire vernal pool landscape; not just the extremes. These reference locations will also remain unchanged during the duration of the five year interim monitoring period. All pools are monitored at the same time, every two weeks during the rainy season, and are collectively referred to as “monitored pools”. Through this comparison of constructed pools with reference pools, the ecological development of constructed habitats can be evaluated against the onsite representative climax vegetation community over time, helping identify the ecological functionality of constructed features and guide adaptive management when needed.”
I smiled as he finished explaining, content that not only was I lucky to enjoy such a unique and beautiful site, but help complete a task vital to its success and the sustainability of the regional ecosystem as a whole.