[in print] Recent Publications from Molly Polk and Robert Bean

Doctoral students Molly Polk and Robert bean have new publications available. Follow the links below for the full text of each article.

Bury, J., Mark, B. G., Carey, M., Young, K. R., McKenzie, J. M., Baraer, M., … Polk, M. H. (2013). New Geographies of Water and Climate Change in Peru: Coupled Natural and Social Transformations in the Santa River Watershed. Annals of the Association of American Geographers, 103(2), 363–374.

Abstract: Projections of future water shortages in the world's glaciated mountain ranges have grown increasingly dire. Although water modeling research has begun to examine changing environmental parameters, the inclusion of social scenarios has been very limited. Yet human water use and demand are vital for long-term adaptation, risk reduction, and resource allocation. Concerns about future water supplies are particularly pronounced on Peru's arid Pacific slope, where upstream glacier recession has been accompanied by rapid and water-intensive economic development. Models predict water shortages decades into the future, but conflicts have already arisen in Peru's Santa River watershed due to either real or perceived shortages. Modeled thresholds do not align well with historical realities and therefore suggest that a broader analysis of the combined natural and social drivers of change is needed to more effectively understand the hydrologic transformation taking place across the watershed. This article situates these new geographies of water and climate change in Peru within current global change research discussions to demonstrate how future coupled research models can inform broader scale questions of hydrologic change and water security across watersheds and regions. We provide a coupled historical analysis of glacier recession in the Cordillera Blanca, declining Santa River discharge, and alpine wetland contraction. We also examine various water withdrawal mechanisms, including smallholder agriculture, mining, potable water use, hydroelectric power generation, and coastal irrigation. We argue that both ecological change and societal forces will play vital roles in shaping the future of water resources and water governance in the region.




Lafrenz, M. D., Bean, R. A., & Uthman, D. (2013). Soil ripening following dam removal. Physical Geography, (ahead-of-print), 1-12.

Abstract: The onset of pedogenesis in dewatered reservoir sediments following a dam removal was evaluated using a ripening index that was initially developed to describe the condition of drained, marine sediments behind Dutch dikes. The drained reservoir exposed lahar terraces, mantled with reservoir sediment, upstream of the former dam at a similar geomorphic position to a downstream lahar terrace. Three years following dam removal, the exposed sediment has physically ripened (n-values are less than 0.7) over 1 m to the depth of a buried soil. However, the sediment has only chemically ripened to a depth of approximately 16 cm, the depth at which pH values become higher than those of the downstream terrace soils. Even at the surface, the sediment has not biologically ripened, as indicated by the low carbon-to-nitrogen ratios (13:1) relative to those of the downstream soil surface (28:1). These results indicate that chemical and biological ripening happen more slowly than physical ripening. As such, dewatered reservoir sediments likely reach field capacity before other crucial edaphic conditions have developed, such as the accumulation of plant-available iron and nitrate. This difference will greatly affect vegetation successional pathways in these newly created upland environments.

Chang, H., Jung, I.-W., Strecker, A., Wise, D., Lafrenz, M., Shandas, V., Bean, R.,...Paris, M (2013). Water Supply, Demand, and Quality Indicators for Assessing the Spatial Distribution of Water Resource Vulnerability in the Columbia River Basin. Atmosphere-Ocean, 1–18.

We investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality. Based on the US county scale, spatial analysis was conducted using various biophysical and socio-economic indicators that control water vulnerability. Water supply vulnerability and water demand vulnerability exhibited a similar spatial clustering of hotspots in areas where agricultural lands and variability of precipitation were high but dam storage capacity was low. The hotspots of water quality vulnerability were clustered around the main stem of the Columbia River where major population and agricultural centres are located. This multiple equal weight indicator approach confirmed that different drivers were associated with different vulnerability maps in the sub-basins of the CRB. Water quality variables are more important than water supply and water demand variables in the Willamette River basin, whereas water supply and demand variables are more important than water quality variables in the Upper Snake and Upper Columbia River basins. This result suggests that current water resources management and practices drive much of the vulnerability within the study area. The analysis suggests the need for increased coordination of water management across multiple levels of water governance to reduce water resource vulnerability in the CRB and a potentially different weighting scheme that explicitly takes into account the input of various water stakeholders.