Details

Autor(en) / Beteiligte

• Ji, L
• Wylie, B K
• Zhang, L
• Rover, J
• Tieszen, L L

Titel

Delineating Surface Water Features In The Prairie Pothole Wetlands With MODIS Data

Ist Teil von

• Eos (Washington, D.C.), 2007-12, Vol.88 (52)

Erscheinungsjahr

2007

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• The Prairie Pothole Region (PPR), covered with thousands of shallow ponds known as potholes, is a large wetland area in central North America. The PPR wetlands are valuable because of the ecosystem services they provide, including water balance and flood mediation, habitat for migratory birds and waterfowl production, and carbon sequestration. During the last century, impacts of intense land use (agricultural and commercial development) and climate change have caused drastic reductions of surface water area and wetland habitat in the PPR. Spatial and temporal characterizations of the surface water dynamics are important for understanding the hydrological and ecological characteristics in the PPR wetlands. In this study, we use the Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data processed as 8-day composites at 500-meter resolution from 2000 to 2006. The modified normalized difference water index [MNDWI = (band 4 --C band 6)/(band 4 + band 6)] was computed to delineate water features. By adjusting the MNDWI threshold, we generated three land-cover classes: water, land, and water/land mixture. Additionally, we acquired 26 Landsat TM/ETM+ scenes, 14 to calibrate the MODIS MDNWI threshold and 12 to independently validate the MODIS water feature products. For the validation, the maps of percent water area derived from MODIS were compared with the maps generated from the Landsat images at a 5-kilometer grid level. The comparison illustrates a low root mean square error (0.0034 percent) and a high correlation coefficient (0.95), suggesting satisfactory accuracy of the MODIS water products. We have produced and illustrated the MODIS water feature maps for the U.S. portion of the PPR at 32-day intervals for the growing seasons from 2000 to 2006. The time series of MODIS-derived water feature maps are useful for delineating water features and monitoring water area dynamics in this area, and these products provide coarse resolution information to support conservation and management across large regions of the PPR wetlands. The development of the technique is also of value in the analysis of water dynamics for different wetland areas, such as the Yukon River Basin in Alaska.