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      <title>Top Downloaded Articles This Week: Water Resources Research</title>
      <link>http://www.agu.org/contents/journals/ViewPublishedToday.do</link>
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      <copyright>AGU</copyright>
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         <title>Catchment hydrological responses to forest harvest amount and spatial pattern</title>
         <link>http://dx.doi.org/10.1029/2010WR010165</link>
         <description><![CDATA[Forest harvest effects on streamflow generation have been well described experimentally, but a clear understanding of process-level hydrological controls can be difficult to ascertain from data alone. We apply a new model, Visualizing Ecosystems for Land Management Assessments (VELMA), to elucidate how hillslope and catchment-scale processes control stream discharge in a small Pacific Northwest catchment. VELMA is a spatially distributed ecohydrology model that links hydrological and biogeochemical processes within watersheds. The study site is WS10 of the H.J. Andrews LTER, a 10 ha forested catchment clearcut in 1975. Simulated and observed daily streamflow are in good agreement for both the pre- (1969–1974) and postharvest (1975–2008) periods (Nash-Sutcliffe efficiency = 0.807 and 0.819, respectively). One hundred scenarios, where harvest amounts ranged from 2% to 100% were conducted. Results show that (1) for the case of a 100% clearcut, stream discharge initially increased by ∼29% or 345 mm but returned to preclearcut levels within 50 years, and (2) annual streamflow increased at a near linear rate of 3.5 mm year−1 for each percent of catchment harvested, irrespective of location. Thereafter, to assess the impact of harvest location on stream discharge, 20 harvest scenarios were simulated, where harvest amount was fixed at 20% but harvest location varied. Results show that the streamflow response is strongly sensitive to harvest distance from the stream channel. Specifically, a 20% clearcut area near the catchment divide resulted in an average annual streamflow increase of 53 mm, whereas a 20% clearcut near the stream resulted in an average annual streamflow increase of 92 mm.]]></description>
         <author>Alex Abdelnour, Marc Stieglitz, Feifei Pan and Robert McKane</author>
         <category>Water Resources Research</category>
         <pubDate>47</pubDate>
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         <title>Correction to “Interannual variability of snowmelt in the Sierra Nevada and Rocky Mountains, United States: Examples from two alpine watersheds”</title>
         <link>http://dx.doi.org/10.1029/2012WR012168</link>
         <description/>
         <author>Steven M. Jepsen, Noah P. Molotch, Mark W. Williams, Karl E. Rittger and James O. Sickman</author>
         <category>Water Resources Research</category>
         <pubDate>48</pubDate>
      </item>
      <item>
         <title>Flow and transport effects of compaction bands in sandstone at scales relevant to aquifer and reservoir management</title>
         <link>http://dx.doi.org/10.1029/2005WR004664</link>
         <description><![CDATA[Thin, tabular, low-porosity, low-permeability compaction bands form pervasive, subparallel, anastomosing arrays that extend over square kilometers of exposure in the Aztec Sandstone of southeastern Nevada, an exhumed analog for active aquifers and reservoirs. In order to examine the potential flow and transport effects of these band arrays at scales relevant to production and management, we performed a suite of simulations using an innovative discrete-feature modeling technique to capture the exact pattern of compaction bands mapped over some 150,000 m2 of contiguous outcrop. Significant impacts related to the presence of the bands and their dominant trend are apparent: the average pressure drop required to drive flow between wells exceeds that for band-free sandstone by a factor of three and is 10% to 50% higher across the bands versus along them; reservoir production efficiency varies up to 56% for a typical five-spot well array, depending on its orientation relative to the dominant band trend; and contaminant transport away from a point source within an aquifer tends to channel along the bands, regardless of the regional gradient direction. We conclude that accounting for the flow effects of similar compaction-band arrays would prove essential for optimal management of those sandstone aquifers and reservoirs in which they occur.]]></description>
         <author>K. R. Sternlof, M. Karimi-Fard, D. D. Pollard and L. J. Durlofsky</author>
         <category>Water Resources Research</category>
         <pubDate>42</pubDate>
      </item>
      <item>
         <title>Simulating streamflow and dissolved organic matter export from a forested watershed</title>
         <link>http://dx.doi.org/10.1029/2011WR011423</link>
         <description><![CDATA[Stream water concentrations of dissolved organic matter (DOM) exhibit large temporal variations during precipitation on forested, headwater catchments. We present a modeling framework appropriate for describing streamflow and event-driven export of DOM from small, forested watersheds. Our model links parametrically simple formulations for rainfall-runoff generation and soil water carbon dynamics. The rainfall-runoff formulation is developed by modifying the catchment model of Kirchner (2009) to account for hysteresis in the relationship between stream discharge and catchment water storage. Time series computations of catchment water storage are used by the soil carbon model to approximate the effects of leaching, adsorption, and mineralization on soil water DOM concentrations and the export of DOM from the terrestrial reservoir to the stream. Our findings show that this model is capable of reproducing hourly variations of stream discharge (ranging from 0.01 to 0.38 mm h−1) and stream water DOM concentrations (ranging from 1.8 to 14 mg C L−1) measured in a forested headwater stream in north central Massachusetts. Our analysis highlights the strong linkage between soil carbon dynamics and hydrological processes that govern catchment water storage and flow paths connecting the terrestrial system to the stream.]]></description>
         <author>Na Xu, James E. Saiers, Henry F. Wilson and Peter A. Raymond</author>
         <category>Water Resources Research</category>
         <pubDate>48</pubDate>
      </item>
      <item>
         <title>River channel slope, flow resistance, and gravel entrainment thresholds</title>
         <link>http://dx.doi.org/10.1029/2011WR010850</link>
         <description><![CDATA[River beds are traditionally assumed to become mobile at a fixed value of nondimensional shear stress, but several flume and field studies have found that the critical value is higher in steep shallow flows. Explanations for this have been proposed in terms of the force balance on individual grains. The trend can also be understood in bulk-flow terms if total flow resistance has “base” and “additional” components, the latter due to protruding immobile grains as well as any bedforms, and the stress corresponding to “additional” resistance is not available for grain movement in threshold conditions. A quantitative model based on these assumptions predicts that critical Shields stress increases with slope, critical stream power is near-invariant with slope, and each has a secondary dependence on bed sorting. The proposed slope dependence is similar to what force-balance models predict and consistent with flume data and most field data. Possible explanations are considered for the inability of this and other models to match the very low critical values of width-averaged stress and power reported for some low-gradient gravel bed rivers.]]></description>
         <author>Robert I. Ferguson</author>
         <category>Water Resources Research</category>
         <pubDate>48</pubDate>
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