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Forested Watersheds (forested + watershed)

Distribution by Scientific Domains

Engineering	81%

Selected Abstracts

PREDICTION OF STREAM TEMPERATURE IN FORESTED WATERSHEDS,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2004
V. Sridhar
ABSTRACT: Removal of streamside vegetation changes the energy balance of a stream, and hence its temperature. A common approach to mitigating the effects of logging on stream temperature is to require establishment of buffer zones along stream corridors. A simple energy balance model is described for prediction of stream temperature in forested headwater watersheds that allows evaluation of the performance of such measures. The model is designed for application to "worst case" or maximum annual stream temperature, under low flow conditions with maximum annual solar radiation and air temperature. Low flows are estimated via a regional regression equation with independent variables readily accessible from GIS databases. Testing of the energy balance model was performed using field data for mostly forested basins on both the west and east slopes of the Cascade Mountains, and was then evaluated using the regional equations for low flow and observed maximum reach temperatures in three different east slope Cascades catchments. A series of sensitivity analyses showed that increasing the buffer width beyond 30 meters did not significantly decrease stream temperatures, and that other vegetation parameters such as leaf area index, average tree height, and to a lesser extent streamside vegetation buffer width, more strongly affected maximum stream temperatures. [source]

Sensitivity of Stream flow and Water Table Depth to Potential Climatic Variability in a Coastal Forested Watershed,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2010
Zhaohua Dai
Dai, Zhaohua, Carl C. Trettin, Changsheng Li, Devendra M. Amatya, Ge Sun, and Harbin Li, 2010. Sensitivity of Streamflow and Water Table Depth to Potential Climatic Variability in a Coastal Forested Watershed. Journal of the American Water Resources Association (JAWRA) 1,13. DOI: 10.1111/j.1752-1688.2010.00474.x Abstract:, A physically based distributed hydrological model, MIKE SHE, was used to evaluate the effects of altered temperature and precipitation regimes on the streamflow and water table in a forested watershed on the southeastern Atlantic coastal plain. The model calibration and validation against both streamflow and water table depth showed that the MIKE SHE was applicable for predicting the streamflow and water table dynamics for this watershed with an acceptable model efficiency (E > 0.5 for daily streamflow and >0.75 for monthly streamflow). The simulation results from changing temperature and precipitation scenarios indicate that climate change influences both streamflow and water table in the forested watershed. Compared to current climate conditions, the annual average streamflow increased or decreased by 2.4% with one percentage increase or decrease in precipitation; a quadratic polynomial relationship between changes in water table depth (cm) and precipitation (%) was found. The annual average water table depth and annual average streamflow linearly decreased with an increase in temperature within the range of temperature change scenarios (0-6°C). The simulation results from the potential climate change scenarios indicate that future climate change will substantially impact the hydrological regime of upland and wetland forests on the coastal plain with corresponding implications to altered ecosystem functions that are dependent on water. [source]

Topographic controls on shallow groundwater dynamics: implications of hydrologic connectivity between hillslopes and riparian zones in a till mantled catchment

HYDROLOGICAL PROCESSES, Issue 16 2010
J. M. Detty
Abstract Hydrologic connectivity is regarded as one of the key controls in determining catchment rainfall,run-off response and has been linked to the export of solutes from uplands to streams. We sought to identify the patterns of hydrologic connectivity within a small forested watershed by monitoring the shallow groundwater fluctuations of simple topographically defined landform sequences (footslope,backslope,shoulder). A spatially distributed instrument network was employed to continuously measure hydrometric responses of the shallow subsurface during seasonal wet-up from summer through winter in a small till mantled research catchment. We demonstrate that the spatial patterns of shallow water table extent and duration, and therefore hydrologic connectivity, had a strong seasonal signature. During the low antecedent soil moisture conditions typically associated with the growing season, water tables were patchy, discontinuous, and only the wettest near-stream footslope areas were consistently hydrologically connected with the stream network. During the dormant season, footslopes and backslopes maintained water tables that persisted between storm events and were almost continuously connected with the stream network. In the largest storm events, the typically driest landforms (shoulder slopes) established shallow transient water tables, suggesting that nearly the entire catchment was temporarily hydrologically connected with the stream network. In addition, we found significant differences (p < 0·05) in the magnitude and duration of groundwater responses to rainfall among landform groups both seasonally and during events. These results have implications for using a similarity approach in representing characteristic hydrologic responses of topographically defined watershed elements, determining hydrologic connectivity between watershed elements, as well as for understanding solute transport in catchments. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Hydrology and water quality in two mountain basins of the northeastern US: assessing baseline conditions and effects of ski area development,,

HYDROLOGICAL PROCESSES, Issue 12 2007
Beverley Wemple
Abstract Mountain regions throughout the world face intense development pressures associated with recreational and tourism uses. Despite these pressures, much of the research on bio-geophysical impacts of humans in mountain regions has focused on the effects of natural resource extraction. This paper describes findings from the first 3 years of a study examining high elevation watershed processes in a region undergoing alpine resort development. Our study is designed as a paired-watershed experiment. The Ranch Brook watershed (9·6 km2) is a relatively pristine, forested watershed and serves as the undeveloped ,control' basin. West Branch (11·7 km2) encompasses an existing alpine ski resort, with approximately 17% of the basin occupied by ski trails and impervious surfaces, and an additional 7% slated for clearing and development. Here, we report results for water years 2001,2003 of streamflow and water quality dynamics for these watersheds. Precipitation increases significantly with elevation in the watersheds, and winter precipitation represents 36,46% of annual precipitation. Artificial snowmaking from water within West Branch watershed currently augments annual precipitation by only 3,4%. Water yield in the developed basin exceeded that in the control by 18,36%. Suspended sediment yield was more than two and a half times greater and fluxes of all major solutes were higher in the developed basin. Our study is the first to document the effects of existing ski area development on hydrology and water quality in the northeastern US and will serve as an important baseline for evaluating the effects of planned resort expansion activities in this area. Published in 2007 by John Wiley & Sons, Ltd. [source]

The impact of storm events on solute exports from a glaciated forested watershed in western New York, USA

HYDROLOGICAL PROCESSES, Issue 16 2006
S. P. Inamdar
Abstract This study analysed the importance of precipitation events from May 2003 to April 2004 on surface water chemistry and solute export from a 696 ha glaciated forested watershed in western New York State, USA. The specific objectives of the study were to determine: (a) the temporal patterns of solutes within individual storm events; (b) the impact of precipitation events on seasonal and annual export budgets; and (c) how solute concentrations and loads varied for precipitation events among seasons as functions of storm intensity and antecedent moisture conditions. Analysis of solute trajectories showed that NH4+, total Al and dissolved organic nitrogen (DON) peaked on the hydrograph rising limb, whereas dissolved organic carbon (DOC) concentrations peaked following the discharge peak. Sulphate and base-cations displayed a dilution pattern with a minimum around peak discharge. End-member mixing analysis showed that throughfall contributions were highest on the rising limb, whereas valley-bottom riparian waters peaked following the discharge peak. The trajectories of NO3, concentrations varied with season, indicating the influence of biotic processes on the generation, and hence flux, of this solute. Storm events had the greatest impact on the annual budgets for NH4+, K+, total dissolved Al, DON and DOC. Storm events during summer had the greatest impact on seasonal solute budgets. Summer events had the highest hourly discharges and high concentrations of solutes. However, NO3, and DOC exports during a spring snowmelt event were considerably more than those observed for large events during other periods of the year. Comparisons among storms showed that season, precipitation amount, and antecedent moisture conditions affected solute concentrations and loads. Concentrations of solutes were elevated for storms that occurred after dry antecedent conditions. Seven of the largest storms accounted for only 15% of the annual discharge, but were responsible for 34%, 19%, 64%, 13%, 39% and 24% of the annual exports of NH4+, K+, Al, NO3,, DON and DOC respectively. These results suggest that the intense and infrequent storms predicted for future climate-change scenarios will likely increase the exports of solutes like DOC, DON, NH4+, Al and K+ from watersheds. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Relationship of topography to surface water chemistry with particular focus on nitrogen and organic carbon solutes within a forested watershed in Hokkaido, Japan

HYDROLOGICAL PROCESSES, Issue 2 2006
Akiko Ogawa
Abstract We studied the relationships between streamwater chemistry and the topography of subcatchments in the Dorokawa watershed in Hokkaido Island, northern Japan, to examine the use of topography as a predictor of streamwater chemistry in a watershed with relatively moderate terrain compared with other regions of Japan. Topographic characteristics of the Dorokawa watershed and its subcatchments were expressed as topographic index (TI) values, which ranged from 4·5 to 20·4 for individual grid cells (50 × 50 m2), but averaged from 6·4 to 7·4 for the 20 subcatchments. Streamwater samples for chemical analyses were collected four times between June and October 2002 from 20 locations in the watershed. The pH of water that passed through the watershed increased from ,5·0 to 7·0, with major increases in Na+ and Ca2+ and marked decreases in NO3, and SO. Distinctive spatial patterns were observed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and NO3, concentrations of streamwater across the watershed. Statistical analyses indicated significant linear relationships between the average TI values of subcatchments and DOC, DON, and NO3, concentrations. Furthermore, the proportion of DOC in streamwaters in the wet season increased with TI values relative to other nitrogen species, whereas NO3, concentrations decreased with TI. The gradients of soil wetness and the presence of wetlands explained many of the observed spatial and temporal patterns of DOC, DON, and NO3, concentrations in the surface waters of the Dorokawa watershed. Our results suggest that the TI is especially useful for predicting the spatial distribution of DOC, DON and NO3, in the surface waters of Hokkaido, where topographical relief is moderate and wetlands more common than in other regions of Japan. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Sensitivity of Stream flow and Water Table Depth to Potential Climatic Variability in a Coastal Forested Watershed,

Forest age, wood and nutrient dynamics in headwater streams of the Hubbard Brook Experimental Forest, NH

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2007
Dana R. Warren
Abstract Instream processing may substantially alter nutrient export from forested watersheds. This study tested how instream uptake of N and P were affected by successional differences in the accumulation of large wood and debris dams in a 66-year chronosequence formed by five watersheds within the Hubbard Brook Experimental Forest (HBEF), NH. Nutrient enrichment releases in summer 1998 were used to measure the uptake velocities of phosphate, nitrate and ammonium for five streams within HBEF, and results indicated that uptake of PO43, was closely associated with forest age. In 2004, we quantified volume and abundance of large wood in each stream to test whether large wood abundance could be linked to nitrate uptake as well as phosphate. The volume of instream wood increased with forest age, at an apparent rate of 0·03 m3 (100 m),1 per year for these early to mid-successional forests (r2 = 0.95); however, debris dam frequency did not. Instead, debris dam frequency, when controlled for stream size, followed a U-shaped distribution, with high dam frequency in very young forests, low frequency in forests around 20,30 years of age and increasing dam frequency again as forests matured. Phosphate uptake velocity increased strongly with both forest age and large wood volume (r2 = 0·99; p < 0·001 in both cases); however, nitrate and ammonium uptake were not related to either factor. We attribute the positive relationship between phosphate uptake velocity and forest age/large wood volume to increased abiotic adsorption of phosphate by the inorganic sediments retained by wood. Nitrogen uptake in these streams is primarily biologically driven and did not vary predictably with these structural features of channels. We expect wood abundance to increase in HBEF streams as the forest matures, with a subsequent increase in stream phosphate uptake capacity. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Analysis of landslide frequencies and characteristics in a natural system, coastal British Columbia

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2004
R. H. Guthrie
Abstract Two hundred and one debris slides and debris ,ows were analyzed in a 286 km2 study area on the west coast of Vancouver Island, British Columbia, Canada. The study area remains essentially untouched by humans and therefore affords a natural setting in which to examine slope processes. Landslides were identi,ed and characterized on aerial photographs from 1:15 000 to 1:31 680, and were then mapped and transferred to a GIS for analysis. Based on detailed landslide surveys, we propose a new method to accurately determine volume of landslides of this type by measured total area. Results indicate average denudation rates of 56 m3 y,1 km,2, and higher natural rates of failure than analogous regions in coastal British Columbia. In contrast, the landslide rates are substantially less than those from forested watersheds. Landslide distribution is spatially clustered in air photograph epochs, and we propose intense storm cells within regional events as the causal mechanism. Further, failures occurred preferentially over the West Coast Crystalline Complex (by 1·4 times), a metamorphic assemblage of gabbros, schists and amphibolites, but 1·5 times less often over the Island Plutonic Suite, a granitic intrusive formation. The former result represents a new ,nding, while the latter corroborates ,ndings of previous authors. We examined magnitude,frequency relationships of the data set and present for the ,rst time a strong argument that the rollover effect is not merely an artefact, but is instead a consequence of the physical characteristics of the landslides themselves. We subsequently analyzed magnitude,frequency relationships from two other complete data sets from coastal British Columbia and produced a family of curves corroborating this result. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Hydrologic comparison between a forested and a wetland/lake dominated watershed using SWAT

HYDROLOGICAL PROCESSES, Issue 10 2008
Kangsheng Wu
Abstract The Soil and Water Assessment Tool (SWAT) is a physically-based hydrologic model developed for agricultural watersheds, which has been infrequently validated for forested watersheds, particularly those with deep overwinter snow accumulation and abundant lakes and wetlands. The goal of this study was to determine the applicability of SWAT for modelling streamflow in two watersheds of the Ontonagon River basin of northern Michigan which differ in proportion of wetland and lake area. The forest-dominated East Branch watershed contains 17% wetland and lake area, whereas the wetland/lake-dominated Middle Branch watershed contains 26% wetland and lake area. The specific objectives were to: (1) calibrate and validate SWAT models for the East Branch and Middle Branch watersheds to simulate monthly stream flow, and (2) compare the effects of wetland and lake abundance on the magnitude and timing of streamflow. Model calibration and validation was satisfactory, as determined by deviation of discharge D and Nash and Sutcliffe coefficient values E that compared simulated monthly mean discharge versus measured monthly mean discharge. Streamflow simulation discrepancies occurred during summer and fall months and dry years. Several snow melting parameters were found to be critical for the SWAT simulation: TIMP (snow temperature lag factor) and SMFMX and SMFMN (melting factors). Snow melting parameters were not transferable between adjacent watersheds. Differences in seasonal pattern of long-term monthly streamflow were found, with the forest-dominated watershed having a higher peak flow during April but a lower flow during the remainder of the year in comparison to the wetland and lake-dominated watershed. The results suggested that a greater proportion of wetland and lake area increases the capacity of a watershed to impound surface runoff and to delay storm and snow melting events. Representation of wetlands and lakes in a watershed model is required to simulate monthly stream flow in a wetland/lake-dominated watershed. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Hydrochemical behaviour of dissolved nitrogen and carbon in a headwater stream of the Canadian Shield: relevance of antecedent soil moisture conditions

HYDROLOGICAL PROCESSES, Issue 3 2008
Julie M. L. Turgeon
Abstract This paper examines the impact of contrasting antecedent soil moisture conditions on the hydrochemical response, here the changes in dissolved nitrogen (NO3,, NH4+ and dissolved organic nitrogen (DON)) and dissolved organic carbon (DOC) concentrations, of a first-order stream during hydrological events. The study was performed in the Hermine, a 5 ha forested watershed of the Canadian Shield. It focused on a series of eight precipitation events (spring, summer and fall) sampled every 2 or 3 h and showing contrasted antecedent moisture conditions. The partition of the eight events between two groups (dry or wet) of antecedent moisture conditions was conducted using a principal component analysis (PCA). The partition was controlled (first axis explained 86% of the variability) by the antecedent streamflow, the streamflow to precipitation ratio Q/P and by the antecedent groundwater depth. The mean H+, NO3,, NH4+, total dissolved nitrogen and DOC concentrations and electrical conductivity values in the stream were significantly higher following dry antecedent conditions than after wetter conditions had prevailed in the Hermine, although the temporal variability was high (17 to 138%). At the event scale, a significantly higher proportion of the changes in DON, NO3,, and DOC concentrations in the stream was explained by temporal variations in discharge compared with the seasonal and annual scales. Two of the key hydrochemical features of the dry events were the synchronous changes in DOC and flow and the frequent negative relationships between discharge and NO3,. The DON concentrations were much less responsive than DOC to changes in discharge, whereas NH was not in phase with streamflow. During wet events, the synchronicity between streamflow and DON or NO3, was higher than during dry events and discharge and NO3, were generally positively linked. Based on these observations, the hydrological behaviour of the Hermine is conceptually compatible with a two-component model of shallow (DON and DOC rich; variable NO3,) and deep (DON and DOC poor; variable NO3,) subsurface flow. The high NO3, and DOC levels measured at the early stages of dry events reflected the contribution from NO3, -rich groundwaters. The contribution of rapid surface flow on water-repellent soil materials located close to the stream channel is hypothesized to explain the DOC levels. An understanding of the complex interactions between antecedent soil moisture conditions, the presence of soil nutrients available for leaching and the dynamics of soil water flow paths during storms is essential to explain the fluxes of dissolved nitrogen and carbon in streams of forested watersheds. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Power function decay of hydraulic conductivity for a TOPMODEL-based infiltration routine

HYDROLOGICAL PROCESSES, Issue 18 2006
Jun Wang
Abstract TOPMODEL rainfall-runoff hydrologic concepts are based on soil saturation processes, where soil controls on hydrograph recession have been represented by linear, exponential, and power function decay with soil depth. Although these decay formulations have been incorporated into baseflow decay and topographic index computations, only the linear and exponential forms have been incorporated into infiltration subroutines. This study develops a power function formulation of the Green and Ampt infiltration equation for the case where the power n = 1 and 2. This new function was created to represent field measurements in the New York City, USA, Ward Pound Ridge drinking water supply area, and provide support for similar sites reported by other researchers. Derivation of the power-function-based Green and Ampt model begins with the Green and Ampt formulation used by Beven in deriving an exponential decay model. Differences between the linear, exponential, and power function infiltration scenarios are sensitive to the relative difference between rainfall rates and hydraulic conductivity. Using a low-frequency 30 min design storm with 4·8 cm h,1 rain, the n = 2 power function formulation allows for a faster decay of infiltration and more rapid generation of runoff. Infiltration excess runoff is rare in most forested watersheds, and advantages of the power function infiltration routine may primarily include replication of field-observed processes in urbanized areas and numerical consistency with power function decay of baseflow and topographic index distributions. Equation development is presented within a TOPMODEL-based Ward Pound Ridge rainfall-runoff simulation. Copyright © 2006 John Wiley & Sons, Ltd. [source]

The effects of log erosion barriers on post-fire hydrologic response and sediment yield in small forested watersheds, southern California,

HYDROLOGICAL PROCESSES, Issue 15 2001
Peter M. Wohlgemuth
Abstract Wildfire usually promotes flooding and accelerated erosion in upland watersheds. In the summer of 1999, a high-severity wildfire burned a series of mixed pine/oak headwater catchments in the San Jacinto Mountains of southern California. Log erosion barriers (LEBs) were constructed across much of the burned area as an erosion control measure. We built debris basins in two watersheds, each about 1 ha in area, one with LEBs, the other without, to measure post-fire hydrologic response and sediment yield and to evaluate the effectiveness of the LEBs. The watersheds are underlain by granitic bedrock, producing a loamy sand soil above large extents of weathered bedrock and exposed core stones (tors) on the surface. Measured soil water-repellency was similar over the two catchments. Rain gauges measured 348 mm of precipitation in the first post-fire year. The ephemeral stream channels experienced surface flow after major rainstorms, and the source of the water was throughflow exfiltration at the slope/channel interface. Post-fire overland flow produced some rilling, but hillslope erosion measured in silt fences away from any LEBs was minor, as was sediment accumulation behind the LEBs. Stream channels in the catchments exhibited minor net scour. Water yield was much greater in the LEB-treated watershed. This resulted in 14 times more sediment yield by weight than the untreated watershed. Average soil depths determined by augering were nearly double in the catchment without the LEBs compared with the treated watershed. This suggests that differences in water and sediment yield between the two catchments are due to the twofold difference in the estimated soil water-holding capacity in the untreated watershed. It appears that the deeper soils in the untreated watershed were able to retain most of the precipitation, releasing less water to the channels and thereby reducing erosion and sediment yield. Thus, the test of LEB effectiveness was inconclusive in this study, because soil depth and soil water-holding capacity may have masked their performance. Published in 2001 John Wiley & Sons, Ltd. [source]

Responses of periphyton and insects to experimental manipulation of riparian buffer width along forest streams

JOURNAL OF APPLIED ECOLOGY, Issue 6 2003
Peter M. Kiffney
Summary 1Riparian trees regulate aquatic ecosystem processes, such as inputs of light, organic matter and nutrients, that can be altered dramatically when these trees are harvested. Riparian buffers (uncut strips of vegetation) are widely used to mitigate the impact of clear-cut logging on aquatic ecosystems but there have been few experimental assessments of their effectiveness. 2Forests along 13 headwater stream reaches in south-western British Columbia, Canada, were clear-cut in 1998, creating three riparian buffer treatments (30-m buffer, 10-m buffer and clear-cut to the stream edge), or left as uncut controls, each treatment having three or four replicates. 3We predicted that periphyton biomass and insect consumers would increase as buffer width decreased, because of increased solar flux. We used two complementary studies to test this prediction. 4In one study, we compared benthic communities before and after logging in all 13 streams; a second study focused on periphyton and insect colonization dynamics over 6-week periods in each of four seasons in four streams, one in each treatment. 5Photosynthetically active radiation, and mean and maximum water temperature, increased as buffer width narrowed. 6Periphyton biomass, periphyton inorganic mass and Chironomidae abundance also increased as buffer width narrowed, with the largest differences occurring in the clear-cut and 10-m buffer treatments. 7Photosynthetically active radiation, water temperature, periphyton biomass and periphyton inorganic mass were significantly greater in the 30-m buffer treatment than in controls during some seasons. 8.,Synthesis and applications. We have shown that a gradient of riparian buffer widths created a gradient in light and temperature that led to non-linear increases in periphyton biomass and insect abundance. For example, Chironomidae abundance was generally greater in the 10-m and 30-m buffer treatments than in controls, whereas this was not always the case in the clear-cut treatment. This pattern may be due to the high sediment content of the periphyton mat in the clear-cut treatment, which potentially limited the response of some insects to increased food resources. Overall, our results indicate that uncut riparian buffers of 30-m or more on both sides of the stream were needed to limit biotic and abiotic changes associated with clear-cut logging in headwater, forested watersheds. [source]