Effects Of Hydrological Changes Research Articles

Developing a module for estimating climate warming effects on hydropower pricing in California

Climate warming is expected to alter hydropower generation in California through affecting the annual stream-flow regimes and reducing snowpack. On the other hand, increased temperatures are expected to increase hydropower demand for cooling in warm periods while decreasing demand for heating in winter, subsequently altering the annual hydropower pricing patterns. The resulting variations in hydropower supply and pricing regimes necessitate changes in reservoir operations to minimize the revenue losses from climate warming. Previous studies in California have only explored the effects of hydrological changes on hydropower generation and revenues. This study builds a long-term hydropower pricing estimation tool, based on artificial neural network (ANN), to develop pricing scenarios under different climate warming scenarios. Results suggest higher average hydropower prices under climate warming scenarios than under historical climate. The developed tool is integrated with California's Energy-Based Hydropower Optimization Model (EBHOM) to facilitate simultaneous consideration of climate warming on hydropower supply, demand and pricing. EBHOM estimates an additional 5% drop in annual revenues under a dry warming scenario when climate change impacts on pricing are considered, with respect to when such effects are ignored, underlining the importance of considering changes in hydropower demand and pricing in future studies and policy making.

Response in the trophic state of stratified lakes to changes in hydrology and water level: potential effects of climate change

To determine how climate-induced changes in hydrology and water level may affect the trophic state (productivity) of stratified lakes, two relatively pristine dimictic temperate lakes in Wisconsin, USA, were examined. Both are closed-basin lakes that experience changes in water level and degradation in water quality during periods of high water. One, a seepage lake with no inlets or outlets, has a small drainage basin and hydrology dominated by precipitation and groundwater exchange causing small changes in water and phosphorus (P) loading, which resulted in small changes in water level, P concentrations, and productivity. The other, a terminal lake with inlets but no outlets, has a large drainage basin and hydrology dominated by runoff causing large changes in water and P loading, which resulted in large changes in water level, P concentrations, and productivity. Eutrophication models accurately predicted the effects of changes in hydrology, P loading, and water level on their trophic state. If climate changes, larger changes in hydrology and water levels than previously observed could occur. If this causes increased water and P loading, stratified (dimictic and monomictic) lakes are expected to experience higher water levels and become more eutrophic, especially those with large developed drainage basins.

Response in the trophic state of stratified lakes to changes in hydrology and water level: potential effects of climate change

Research Article| March 01 2011 Response in the trophic state of stratified lakes to changes in hydrology and water level: potential effects of climate change Dale M. Robertson; Dale M. Robertson 1US Geological Survey, 8505 Research Way, Middleton, Wisconsin, USA Tel.: +608-821-3867 Fax: +608-821-3817; E-mail: dzrobert@usgs.gov Search for other works by this author on: This Site PubMed Google Scholar William J. Rose William J. Rose 1US Geological Survey, 8505 Research Way, Middleton, Wisconsin, USA Search for other works by this author on: This Site PubMed Google Scholar Journal of Water and Climate Change (2011) 2 (1): 1–18. https://doi.org/10.2166/wcc.2011.026 Article history Received: December 29 2009 Revision Received: December 13 2010 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll JournalsThis Journal Search Advanced Search Citation Dale M. Robertson, William J. Rose; Response in the trophic state of stratified lakes to changes in hydrology and water level: potential effects of climate change. Journal of Water and Climate Change 1 March 2011; 2 (1): 1–18. doi: https://doi.org/10.2166/wcc.2011.026 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex To determine how climate-induced changes in hydrology and water level may affect the trophic state (productivity) of stratified lakes, two relatively pristine dimictic temperate lakes in Wisconsin, USA, were examined. Both are closed-basin lakes that experience changes in water level and degradation in water quality during periods of high water. One, a seepage lake with no inlets or outlets, has a small drainage basin and hydrology dominated by precipitation and groundwater exchange causing small changes in water and phosphorus (P) loading, which resulted in small changes in water level, P concentrations, and productivity. The other, a terminal lake with inlets but no outlets, has a large drainage basin and hydrology dominated by runoff causing large changes in water and P loading, which resulted in large changes in water level, P concentrations, and productivity. Eutrophication models accurately predicted the effects of changes in hydrology, P loading, and water level on their trophic state. If climate changes, larger changes in hydrology and water levels than previously observed could occur. If this causes increased water and P loading, stratified (dimictic and monomictic) lakes are expected to experience higher water levels and become more eutrophic, especially those with large developed drainage basins. climate change, eutrophication, hydrology, productivity, water level This content is only available as a PDF. © US Geological Survey 2011 You do not currently have access to this content.

Erosion control and protection from torrential floods in Serbia-spatial aspects

Torrential floods represent the most frequent phenomenon within the category of ?natural risks? in Serbia. The representative examples are the torrential floods on the experimental watersheds of the rivers Manastirica (June 1996) and Kamisna (May 2007). Hystorical maximal discharges (Qmaxh) were reconstructed by use of ?hydraulics flood traces? method. Computations of maximal discharges (Qmaxc), under hydrological conditions after the restoration of the watersheds, were performed by use of a synthetic unit hydrograph theory and Soil Conservation Service methodology. Area sediment yields and intensity of erosion processes were estimated on the basis of the ?Erosion Potential Method?. The actual state of erosion processes is represented by the coefficients of erosion Z=0.475 (Manastirica) and Z=0.470 (Kamisna). Restoration works have been planned with a view to decreasing yields of erosive material, increasing water infiltration capacity and reducing flood runoff. The planned state of erosion processes is represented by the coefficients of erosion Z=0.343 (Manastirica) and Z=0.385 (Kamisna). The effects of hydrological changes were estimated by the comparison of historical maximal discharges and computed maximal discharges (under the conditions after the planned restoration). The realisation of restoration works will help decrease annual yields of erosive material from W?=24357 m3 to W?=16198.0 m3 (Manastirica) and from W?=19974 m3 to W?=14434 m3 (Kamisna). The values of historical maximal discharges (QmaxhMan=154.9 m3?s-1; QmaxhKam=76.3 m3?s-1) were significantly decreased after the restoration (QmaxcMan=84.5 m3 ?s-1; QmaxcKam=43.7 m3?s-1), indicating the improvement of hydrological conditions, as a direct consequence of erosion and torrent control works. Integrated management involves biotechnical works on the watershed, technical works on the hydrographic network within a precisely defined administrative and spatial framework in order to achieve maximum security for people and their property and to meet other requirements such as: environmental protection, sustainable soil usage, drinking water supply, rural development, biodiversity sustaining, etc. The lowest and the most effective level is attained through PAERs (Plans for announcement of erosive regions) and PPTFs (Plans for protection from torrential floods), with HZs (Hazard zones) and TAs (Threatened areas) mapping on the basis of spatial analysis of important factors in torrential floods formation. Solutions defined through PAERs and PPTFs must be integrated into Spatial Plans at local and regional levels.

Do changes in flood pulse duration disturb soil carbon dioxide emissions in semi-arid floodplains?

In semi-arid floodplains the average times between floods have been cited to drive metabolic and biogeochemical responses during the subsequent flooding pulse. However, the interaction effects of flood pulse duration and the length of time between floods on the carbon budget are not well understood. Using field experiments, flood pulses—dry cycles were simulated (SF plots—short flood/dry cycles: 15 flood days + 7 dry + 15 flood and LF plots—long flood/dry cycles: 21 flood + 14 dry + 21 flood) in a semi-arid floodplain in Central Spain, in order to study the effects on soil CO2 emissions. Differences on soil water content among SF, LF and control plots were statistically significant throughout the experiment (p < 0.01). Soil CO2 emission rates during drying time were significantly related with the duration of previous flooding and inter-flooding intervals (R2 = 0.52–0.64, p = 0.03). During the first stage of desiccation, the high soil water content appears to limit aerobic metabolism. Soil respiration rates similar to those of control plots measurements occurred 1–2 weeks later. Then, soil respiration increased to a maximum rate which was delayed 5–8 weeks, as high soil water content limited microbial activity. While more than 7 days of inundation promoted denitrification, organic nutrients supplied by flood water increased 1% soil respiration during drying. Differences between SF and LF plots in soil CO2 emissions only appeared after floodplain soil had been subjected to two consecutive flood-dry cycles; 70 days after the second inundation ended, CO2 fluxes achieved similar values in all treatments. Daily soil CO2 emission rates during the entire study period (117 days) were comparable, independently of the flood duration and the time between floods (75.76 ± 1.59 and 77.94 ± 0.45 mmol CO2 m−2 day−1, in SF and LF, respectively). Flood disturbance affects site-specific microbial processes, but only during very short time periods. The mechanism by which soil microbial communities cope or adapt to new conditions needs to be reassessed in future research in order to determine the long-term effects of hydrological changes in the soil carbon balance of semi-arid floodplains.

An ecosystem model‐based estimate of changes in water availability differs from water proxies that are commonly used in species distribution models

ABSTRACTAim To assess whether the water availability measures commonly used in species distribution models might be misleading because they do not account for the hydrological effects of changes in vegetation structure and functioning.Location Europe.Methods We compared different methods for estimating water availability in species distribution models with the soil water content predicted by a process‐based ecosystem model. The latter also accounted for the hydrological effects of dynamic changes in vegetation structure and functioning, including potential physiological effects of increasing CO2.Results All proxies showed similar patterns of water availability across Europe for current climate, but when projected into the future, the changes in the simpler water availability measures showed no correlation with those projected by the more complex ecosystem model, even if CO2 effects were switched off.Main conclusions Results from species distribution modelling studies concerning future changes in species ranges and biodiversity should be interpreted with caution, and more process‐based representations of the water balance of terrestrial ecosystems should be considered within these models.

Hydrological impact assessment of afforestation and change in tree-species composition – A regional case study for the Federal State of Brandenburg (Germany)

Policy changes are often implemented without the assessment of their full environmental impact. We investigate the hydrological effects of changes in forest area triggered by shifts in European agricultural policy, and changes in species composition caused by decisions of regional forest authorities. The scenarios were modelled for the Federal State of Brandenburg (Germany) on a 50 m grid scale using the SWIM (Soil Water Integrated Model) model utilising spatially-explicit land-use patterns. The results suggest a negative impact of afforestation on abandoned arable land (9.4% total state area) on the regional water balance, causing an increase in mean annual evapotranspiration of 3.7% at 100% afforestation when compared to no afforestation. The relatively small annual change covers a much more pronounced seasonal effect, leading to an increase in evapotranspiration by 25.1% in spring with a strong feedback to other hydrological components. In contrast, a change in species composition in existing forest (29.2% total state area) from predominantly Scots Pine to Common Oak decreased the evapotranspiration by 3.4%, accompanied by a much weaker but apparent seasonal pattern. The changes show a high spatial heterogeneity that is masked by a linear mean response for the total state area.

Climate change and the EU Water Framework Directive: how to deal with indirect effects of changes in hydrology on water quality and ecology?

In order to set ecological goals and determine measures for the European Water Framework Directive, the effects of climate change on lake ecosystems should be estimated. It is thought that the complexity of lake ecosystems makes this effect inherently unpredictable. However, models that deal with this complexity are available and well calibrated and tested. In this study we use the ecosystem model PCLake to demonstrate how climate change might affect the ecological status of a shallow peaty lake in 2050. With the model PCLake, combined with a long-term water and nutrient balance, it is possible to describe adequately the present status of the lake. Simulations of future scenarios with increasing precipitation, evaporation and temperature, showed that climate change will lead to higher nutrient loadings. At the same time, it will lead to lower critical loadings. Together this might cause the lake to shift easier from a clear water to a turbid state. The amount of algae, expressed as the concentration Chl-a, will increase, as a consequence turbidity will increase. The outcome of this study; increasing stability of the turbid state of the lake, and thus the need for more drastic measures, is consistent with some earlier studies.

A simulation model of morphological, vegetation and sediment changes in ephemeral streams

AbstractA model to simulate channel changes in ephemeral river channels and to test the effects of hydrological changes due to climate change and[sol ]or land use change was developed under the auspices of the EU funded MEDALUS programme (Mediterranean Desertification and Land Use). The model, CHANGISM (Channel Change GIS Simulation Model), is designed to simulate the effect of channel flow events and of climate conditions on morphology, sediment and vegetation, through sequences of events and conditions, over periods of up to several decades. The modelling is based on cellular automata but with calculations for water and sediment continuity. Process rules have both deterministic and stochastic elements. An important feature of the model is that it incorporates feedback elements between each event. The main aim of the model is to indicate the likely outcomes of events and combinations of conditions. It is linked to GIS for both input and output. The modelling is based on a channel reach and state is input as GIS layers of morphology (DEM), sediment and vegetation cover and state. Other initial conditions of soil moisture, groundwater level, and overall gradient are input. Parameters for processes are read from tables and can be easily changed for successive runs of the model. The bases for decisions on process specifications are discussed in this paper. Initial tests of the operation and sensitivity of the model were made on idealized reaches. The model was then tested using data from monitored sites in SE Spain. Simulations using clearwater flow worked well but initial simulations using events with sediment loads showed some tendency for excess deposition. Further tests and modifications are taking place. Overall, the model is one of the most sophisticated that simulates the interaction of flows with sediment and vegetation and the outcomes in terms of erosion, deposition, morphology, sediment cover, vegetation cover and plant survival over periods of up to 30 years for the scale of a channel reach. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Use of deformation monitoring results in solving geomechanical problems—case studies

Deformation analysis of any type of a deformable body includes geometrical analysis and physical interpretation. The ultimate goal of the geometrical analysis is to determine in the whole deformable object the displacement and strain fields in the space and time domains. Physical interpretation is to establish the relationship between the causative factors (loads) and the deformations. The latter may be obtained by deterministic modelling of deformations using, for example, finite element method (FEM). By comparing the geometrical and deterministic model of deformations, one can verify the designed behaviour of the deformable object. In addition, with properly designed monitoring surveys, one may also determine the actual deformation mechanism and explain causes of deformation in a case of unexpected behaviour of the investigated object. Thus, the role of deformation monitoring surveys becomes much broader than just the conventional determination of the geometrical status of the deformable object. In this presentation two examples are given on the use of geodetic monitoring surveys in the (a) determination of effects of hydrological changes on ground subsidence in a potash mine in Canada and (b) verification of geomechanical parameters of a large earth dam in California during the filling up of the water reservoir.

Cutoffs galore!: occurrence and causes of multiple cutoffs on a meandering river

The creation of cutoffs and of oxbow lakes is a well-known phenomenon of meandering rivers, but views on the extent to which they are inherent in meander behaviour have varied. Assumptions of meander behaviour have shifted from those of stability and equilibrium to recognition of gradual evolution and increased complexity of form. Alternative explanations of cutoff occurrence are discussed here in relation to a remarkable set of cutoffs that occurred in one reach of the River Bollin, UK, for which long-term historical evidence of meander evolution existed and which has been monitored for change and processes over the last 20 years. The cutoffs occurred during the high floods of winter 2000–2001. A series of hypotheses is examined, including the occurrence of floods and effects of hydrological changes. Although the flood events actually caused the cutoffs, the long-term pattern accords with ideas of chaotic behaviour and sinuosity of a river reaching a critical state at which clustering of meander cutoffs takes place. It is suggested that the occurrence of the cutoffs can be explained as inherent in meander behaviour.

Modeling effects of hydrological changes on the carbon and nitrogen balance of oak in floodplains.

We extended the applicability of the ecosystem model BIOME-BGC to floodplain ecosystems to study effects of hydrological changes on Quercus robur L. stands. The extended model assesses floodplain peculiarities, i.e., seasonal flooding and water infiltration from the groundwater table. Our interest was the tradeoff between (a). maintaining regional applicability with respect to available model input information, (b). incorporating the necessary mechanistic detail and (c). keeping the computational effort at an acceptable level. An evaluation based on observed transpiration, timber volume, soil carbon and soil nitrogen content showed that the extended model produced unbiased results. We also investigated the impact of hydrological changes on our oak stands as a result of the completion of an artificial canal network in 1971, which has stopped regular springtime flooding. A comparison of the 11 years before versus the 11 years after 1971 demonstrated that the hydrological changes affected mainly the annual variation across years in leaf area index (LAI) and soil carbon and nitrogen sequestration, leading to stagnation of carbon and nitrogen stocks, but to an increase in the variance across years. However, carbon sequestration to timber was unaffected and exhibited no significant change in cross-year variation. Finally, we investigated how drawdown of the water table, a general problem in the region, affects modeled ecosystem behavior. We found a further amplification of cross-year LAI fluctuations, but the variance in soil carbon and nitrogen stocks decreased. Volume increment was unaffected, suggesting a stabilization of the ecosystem two decades after implementation of water management measures.

WATERSHED-SCALE HYDROLOGIC AND NONPOINT-SOURCE POLLUTION MODELS: REVIEW OF MATHEMATICAL BASES

A clear understanding of a model is important for its appropriate use. In this article, eleven watershed scalehydrologic and nonpoint-source pollution models are reviewed: AGNPS, AnnAGNPS, ANSWERS, ANSWERS-Continuous,CASC2D, DWSM, HSPF, KINEROS, MIKE SHE, PRMS, and SWAT. AnnAGNPS, ANSWERS-Continuous, HSPF, and SWATare continuous simulation models useful for analyzing long-term effects of hydrological changes and watershed managementpractices, especially agricultural practices. AGNPS, ANSWERS, DWSM, and KINEROS are single rainfall event modelsuseful for analyzing severe actual or design single-event storms and evaluating watershed management practices, especiallystructural practices. CASC2D, MIKE SHE, and PRMS have both long-term and single-event simulation capabilities.Mathematical bases, the most important and critical elements of these mathematical models, were identified and compiled.In this article, a comprehensive summary of the compilation is presented in tabular form. The flow-governing equations andtheir solution methods used in each of the eleven models are discussed. The compilation of the mathematical bases of thesemodels would be useful to determine the problems, situations, or conditions for which the models are most suitable, theaccuracies and uncertainties expected, their full potential uses and limitations, and directions for their enhancements or newdevelopments. AGNPS, AnnAGNPS, DWSM, HSPF, MIKE SHE, and SWAT were found to have all the three major components(hydrology, sediment, and chemical) applicable to watershed-scale catchments. SWAT is a promising model for continuoussimulations in predominantly agricultural watersheds, and HSPF is promising for mixed agricultural and urban watersheds.Among the single-event models, DWSM provides a balance between the simple but approximate and the computationallyintensive models and, therefore, is a promising storm event model for agricultural watersheds.

Effects of land‐cover changes on the hydrological response of interior Columbia River basin forested catchments

AbstractThe topographically explicit distributed hydrology–soil–vegetation model (DHSVM) is used to simulate hydrological effects of changes in land cover for four catchments, ranging from 27 to 1033 km2, within the Columbia River basin. Surface fluxes (stream flow and evapotranspiration) and state variables (soil moisture and snow water equivalent) corresponding to historical (1900) and current (1990) vegetation are compared. In addition a sensitivity analysis, where the catchments are covered entirely by conifers at different maturity stages, was conducted. In general, lower leaf‐area index (LAI) resulted in higher snow water equivalent, more stream flow and less evapotranspiration. Comparisons with the macroscale variable infiltration capacity (VIC) model, which parameterizes, rather than explicitly represents, topographic effects, show that runoff predicted by DHSVM is more sensitive to land‐cover changes than is runoff predicted by VIC. This is explained by model differences in soil parameters and evapotranspiration calculations, and by the more explicit representation of saturation excess in DHSVM and its higher sensitivity to LAI changes in the calculation of evapotranspiration. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Estimating the Indirect Effects of Hydrologic Change on Wetland Loss: If the Earth Is Curved, Then How Would We Know It?

Estimating the Indirect Effects of Hydrologic Change on Wetland Loss: If the Earth Is Curved, Then How Would We Know It?

Patterns and Processes of Wetland Loss in Coastal Louisiana Are Complex: A Reply to Turner 2001. Estimating the Indirect Effects of Hydrologic Change on Wetland Loss: If the Earth Is Curved, Then How Would We Know It?

Patterns and Processes of Wetland Loss in Coastal Louisiana Are Complex: A Reply to Turner 2001. Estimating the Indirect Effects of Hydrologic Change on Wetland Loss: If the Earth Is Curved, Then How Would We Know It?

Recent (1995-1998) Canadian research on contemporary processes of river erosion and sedimentation, and river mechanics

Canadian research on contemporary erosion and sedimentation processes covers a wide range of scales, processes, approaches and environmental problems. This review of recent research focuses on the themes of sediment yield, land-use impact, fine-sediment transport, bed material transport and river morphology and numerical modelling of fluvial landscape development. Research on sediment yield and denudation has confirmed that Canadian rivers are often dominated by riparian sediment sources. Studies of the effects of forestry on erosion, in-stream sedimentation and habitat are prominent, including major field experimental studies in coastal and central British Columbia. Studies of fine-sediment transport mechanisms have focused on the composition of particles and the dynamics of flocculation. In fluvial dynamics there have been important contributions to problems of turbulence-scale flow structure and entrainment processes, and the characteristics of bedload transport in gravel-bed rivers. Although much of the work has been empirical and field-based, results of numerical modelling of denudational processes and landscape development also have begun to appear. The nature of research in Canada is driven by the progress of the science internationally, but also by the nature of the Canadian landscape, its history and resource exploitation. Yet knowledge of Canadian rivers is still limited, and problems of, for example, large pristine rivers or rivers in cold climates, remain unexplored. Research on larger scale issues of sediment transfer or the effects of hydrological change is now hampered by reductions in national monitoring programmes. This also will make it difficult to test theory and assess modelling results. Monitoring has been replaced by project- and issues-based research, which has yielded some valuable information on river system processes and opened opportunities for fluvial scientists. However, future contributions will depend on our ability to continue with fundamental fluvial science while fulfilling the management agenda. Copyright © 2000 John Wiley & Sons, Ltd.

Quantifying impacts to riparian wetlands associated with reduced flows along the Greybull River, Wyoming

Reductions in river flows associated with hydrologic changes from diversions may reduce water elevations and impact hydrology of riparian wetlands. The U.S. Army Corps of Engineers and other federal agencies currently do not have appropriate tools to evaluate effects of hydrologic changes on wetlands. We describe use of HEC-RAS modeling to predict and quantify wetland impacts along 10 km of the Greybull River, Wyoming, USA following a proposed 28,313 L/sec diversion for a new off-channel reservoir. Riparian wetlands were delineated and mapped on aerial photographs and topographic maps. A water-surface-profile model of the river was developed using the HEC-RAS model. Floodplain boundaries with and without the diversion were plotted to the same scale and overlaid on the wetland maps to estimate area of wetlands that would not be flooded under the reduced flow model. The model predicted that total area flooded under the 28,313 L/sec diversion in the reach analyzed would be reduced from 167.2 to 149.7 ha and that approximately 0.47 ha of wetland would be impacted by the diversion. We believe that the procedure we used is a valid method to quantify effects of diversion on riparian wetlands and that this procedure should be further evaluated as a method to assess wetland impacts on similar projects.

Effects of hydrologic changes on aboveground production and surface water chemistry in two boreal peatlands in Alberta: Implications for global warming

Aboveground net primary production (NPP) and surface water chemistryvariables were monitored in a lacustrine sedge fen and a bog for four years.There were no significant differences in precipitation, mean growing seasonannual temperature, and number of growing degree days from 1991 to 1994. Themean annual water levels in the lacustrine sedge fen differed significantly,whereas they were similar in the bog during these four years. We measured 15surface water variables in the lacustrine sedge fen and the bog, and foundthat only two correlated significantly with water level fluctuations. In thelacustrine sedge fen, calcium correlated positively (r2= 0.56) and nitrate correlated negatively (r2 =0.20) with water levels. In the bog, potassium correlated positively(r2 = 0.88) and total dissolved phosphorus correlatednegatively (r2 = 0.62) with water levels. The remainingchemical variables showed no significant correlations with water levelfluctuations. Net primary production of the different vegetation strataappeared to respond to different environmental variables. In the lacustrinesedge fen, graminoid production was explained to a significant degree bywater levels (r2 = 0.53), whereas shrub production wasexplained to a significant degree by surface water chemistry variables, suchas nitrate (r2 = 0.74) and total phosphorus(r2 = 0.22). In the bog, temperature was the onlyvariable that explained moss production to a significant degree(r2 = 0.71), whereas ammonium explained graminoidproduction (r2 = 0.66) and soluble reactive phosphorusexplained shrub production to significant degrees (r2 =0.71). There are few direct data on the impact of climatic warming in borealwetlands, although paleoecological and 2×CO2 model datahave provided some indications of past and possibly future changes invegetation composition, respectively. Our results suggest that thelacustrine sedge fen may succeed to a bog dominated by Sphagnum spp. andPicea mariana, whereas the bog may succeed to an upland-type forestecosystem.

Hydrologic restoration of coastal wetlands

Hydrologic modification of coastal wetlands is pervasive, continuing and longstanding in the US. Appreciation for the subtleties of the direct and indirect effects of hydrologic changes on emergent vegetation, soils and co-dependent flora and fauna is contributing to restoration efforts. However the results of wetland restoration/rehabilitation are moslty empirical, rather than scientific in understanding. Science is contributing to the management interest by providing documentation of the past and present failures and successes, and, unveiling the fundamental understanding necessary to move from one wetland to another in an informed and adaptable manner. The papers in this volume are introduced within this framework.