Konstruerede vådområders indvirken på vandløbskvaliteten nedstrøms. Et case-studie af Torsted Sø og -Bæk.

Simonsen, Daniel Palm

4. semester

Miljøteknologi (cand.polyt.), Kandidat

2017

2017-06-09

Torsted Lake is a constructed denitrifying wetland area and lake in Denmark that was established in November 2016. Little is known about how wetlands like these affect the downstream river ecology. The aim of this research was to adress whether there is an impact on the small downstream Torsted Creek as a result of the wetland establishment. Flow rate, chlorophyll-a, organic carbon, temperature, oxygen, pH, conductivity, and sediment erosion were measured in the creek prior, during, and after the wetland establishment. The results show that water quality in Torsted Creek decreased in the first 6 months after the wetland establishment. The descrease of water quality was most distinct i spring. The organic carbon concentration increased by 4 mg/l due to algal blooms in the wetland, raising pH levels to over 9 due to algal uptake of carbonate. The temperature increased by up to 2,5C compared to upstream conditions, and Torsted Creek endured four months of heavy sediment erosion washing out from an established rapid at the outlet of the wetland. Most inorganic particles of >0,063 mm were held back in a grid trap further downstream. Downstream of the main sampling locations, an additional 1st order creek (Aarestrup Creek) flows into Torsted Creek, diluting the physical and chemical effects of temperature, organic carbon, and pH caused by the wetland. In conclusion, the wetland to date has negatively impacted the water quality downstream giving Torsted Creek a deteriorated base of achieving its own environmental goals.

vandløb ; vådområder ; vandkvalitet ; torsted ; vandføring ; klorofyl ; toc ; temperatur ; ilt ; ph ; konduktivitet ; erosion

Download
Vis denne rapport i AAU Studenterprojekter