Development of constructed wetlands in agricultural landscapes using remote sensing techniques

ABSTRACT In Sweden, drainage and the construction of water infrastructure have influenced agriculture in the last few centuries both positively and negatively. Recently, a trend has set in where wetlands are constructed to retain water, retain and reduce nutrients and to enhance the biodiversity. This study aimed to use remote sensing techniques to study landscape water retention over time. In this pilot study, water retention structures in Gotland (57°28′35.0′′N18°29′ 13.9′′E) and Kalmar Län (56°39′41′′N16°21′46′′E) for 2000/2001 and 2020 were identified and analyzed using Landsat data. In this study, it was found that the number of water retention structures (>0.8 ha) increased from 44 to 101 for Gotland Län and from 44 to 127 for Kalmar Län. Most water retention structures were <4 ha and were located in mid- and downstream areas. A comparison of the remote sensed results with the Swedish Meteorological and Hydrological Institute (SMHI) database showed a disagreement of the spatial coordinates of the wetlands in the database with the water retention structures. This pilot study has shown that remote sensed data can be used to identify water retention structures, although higher resolution imagery would be highly advisable in these kinds of studies.