ARCTIC ANTARCTIC AND ALPINE RESEARCH

Applying the index of watershed integrity to the Matanuska-Susitna basin
Aho KB, Flotemersch JE, Leibowitz SG, LaCroix MA and Weber MH
The Matanuska-Susitna Borough is the fastest growing region in the State of Alaska and is impacted by a number of human activities. We conducted a multiscale assessment of the stressors facing the borough by developing and mapping the Index of Watershed Integrity (IWI) and Index of Catchment Integrity (the latter considers stressors in areas surrounding individual stream segments exclusive of upstream areas). The assessment coincided with the borough's stormwater management planning. We adapted the list of anthropogenic stressors used in the original conterminous United States IWI application to reflect the borough's geography, human activity, and data availability. This analysis also represents an early application of the NHDPlus High Resolution geospatial framework and the first use of the framework in an IWI study. We also explored how remediation of one important stressor, culverts, could impact watershed integrity at the catchment and watershed scales. Overall, we found that the integrity scores for the Matanuska-Susitna basin were high compared to the conterminous United States. Low integrity scores did occur in the rapidly developing Wasilla-Palmer core area. We also found that culvert remediation had a larger proportional impact in catchments with fewer stressors.
The water balance of grassland ecosystems in the Austrian Alps
Wieser G, Hammerle A and Wohlfahrt G
The altitudinal variation of precipitation, evapotranspiration and runoff was quantified at 16 different grassland sites between 580 and 2550 m a.s.l. in the Austrian Alps. Along this altitudinal transect annual evapotranspiration decreased from roughly 690 mm at low elevation sites to 210 - 220 mm at the upper limit of the alpine grassland belt. A detailed analysis of the data showed that the observed reduction in the annual sum of evapotranspiration could be mainly explained by the altitudinal decline of the length of the snow free period (i.e. the vegetation period). Daily mean sums of evapotranspiration showed no altitudinal trend and averaged 2.2 mm d independent of elevation, although the leaf area index, growing season mean air temperature, and vapour pressure deficit declined with increasing altitude. As precipitation increased with elevation, evapotranspiration seems to be of secondary importance when compared to runoff. Inter-annual variability of evapotranspiration was fairly low across contrasting dry and wet years (coefficient of variation = 7 %), indicating that even during dry years water availability was not limiting evapotranspiration.