Catchment Management (catchment + management)

Distribution by Scientific Domains
Life Sciences50%

Selected Abstracts

The sensitivity of phytoplankton in Loch Leven (U.K.) to changes in nutrient load and water temperature

FRESHWATER BIOLOGY, Issue 1 2008
J. ALEX ELLIOTT
Summary 1. Loch Leven is a shallow, eutrophic lake in Scotland, U.K. It has experienced much change over the 30 years that it has been studied; this has primarily been due to reduced nutrient loads to the lake through active catchment management. Its recovery has been slow and, therefore, we used a phytoplankton community model (PROTECH) to test its sensitivity to changing nutrient loads and water temperature. 2. PROTECH was initialized to simulate the observed phytoplankton community in 1995 and was then repeatedly run through a combination of step-wise changes in water temperature and nutrient load (two treatments were simulated for nutrient load: one changing both nitrate and phosphorus, and one changing just phosphorus). The effect on total chlorophyll- a concentration, cyanobacteria abundance and phytoplankton diversity was examined. 3. Whilst changes in temperature had little effect, variations in the nutrient load produced a range of responses. Increasing only the phosphorus load caused a large increase in Anabaena abundance and total chlorophyll- a concentration. However, the opposite response was recorded when nitrate load was changed as well, with Anabaena increasing its biomass under reduced nutrient load scenarios. 4. The key factor determining the type of response appeared to be nitrogen availability. Anabaena, a nitrogen fixer, could exploit the phosphorus resource of Loch Leven under limiting nitrogen conditions, allowing it to dominate under most of the scenarios tested apart from those supplying extra nitrogen to the lake. The model predictions agree with the observed data, which show that Anabaena continues to dominate the summer phytoplankton bloom in Loch Leven despite the considerable reduction in phosphorus supply from the catchment. This research provides a possible explanation for this. [source]

The systematic approach to flooding problems,

IRRIGATION AND DRAINAGE, Issue S1 2006
J. (Hans) van Duivendijk
maîtrise des crues; mesures non-structurelles; gestion des inondations Abstract Since 1987 one of the working groups of the International Commission on Irrigation and Drainage (ICID) has, inter alia, been preparing two manuals concerning approaches to flooding problems. The Manual on Non-Structural Approaches to Flood Management was issued in 1999 while the Manual on the Planning of Structural Approaches to Flood Management has been issued recently (2005). In this paper a broad outline of both manuals is presented. The first manual describes in detail the various planning and response measures in flood management, which are known as non-structural measures. The latter are measures which alter the exposure of life and property to flooding but do not change the flood(ing) phenomenon as such. The said planning and response measures comprise such actions as floodplain land use management, flood forecasting and warning, flood fighting, flood proofing, etc. It is explained that such measures are sometimes the only ones feasible in the prevailing circumstances and that, moreover, non-structural measures should always be added to the so-called structural measures if the latter are considered feasible (i.e. feasible from a technical, economic, socio-economic and ecological point of view). In the second manual a methodology is presented for the planning of structural measures. This type of measure alters the physical characteristics of the floods and in this connection one must think of the operation of flood storage reservoirs, upstream catchment management, modification to river channels, construction of levees, special flood diversion channels (bypasses) and operation of hydraulics works. The idea behind this methodology is that it is difficult for planners and decision makers to select the appropriate flood protection system for a given situation including a range of possible floods if the problem is not approached in a systematic manner. Copyright © 2006 John Wiley & Sons, Ltd. Depuis 1987 un des groupes de travail de la CIID prépare, entre autres, deux manuels sur la manière d'approcher les problèmes d'inondation. Le ,Manuel d'approche non-structurelle de la gestion des crues' a été publié en 1999, tandis que le ,Manuel de la planification de l'approche structurelle de la gestion des crues' a été publié plus récemment (2005). Le présent article présente une vue d'ensemble de ces deux manuels. Le premier manuel donne une description détaillée des différentes mesures de préparation et de réponse à la gestion des crues, connues comme étant non-structurelles. Ces mesures changent l'exposition de la vie et des propriétés aux inondations mais ne modifient pas le phénomène proprement dit des crues et des inondations. Elles comprennent des actions telles que la gestion de l'espace dans les plaines d'inondations, les prévisions et alertes, la lutte contre les crues, la protection contre les inondations, etc. On y explique que ces mesures sont parfois les seules faisables dans les circonstances données et que, en outre, des mesures non-structurelles devraient toujours être ajoutées aux mesures dites structurelles si ces dernières sont considérées comme faisables (c'est-à-dire faisables d'un point de vue technique, économique, socio-économique et écologique). Dans le second manuel une méthodologie est présentée pour la planification des mesures structurelles. Ce type de mesures modifie les caractéristiques physiques des crues, comme par exemple réservoirs d'écrétage de crue, gestion des hauts bassins, modification des lits des fleuves, construction de digues, canaux spéciaux de déviation des crues (courts circuits) et fonctionnement d'ouvrages hydrauliques. L'idée qui est derrière cette méthodologie est qu'il est difficile aux planificateurs et aux décideurs de choisir le système de protection contre les crues correspondant exactement à une situation comprenant une large gamme d'inondations possibles si le problème n'est pas approché de manière systématique. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Current issues with fish and fisheries: editor's overview and introduction

JOURNAL OF APPLIED ECOLOGY, Issue 2 2003
S. J. Ormerod
Summary 1.,By any measure, fishes are among the world's most important natural resources. Annual exploitation from wild populations exceeds 90 million tonnes, and fish supply over 15% of global protein needs as part of total annual trade exceeding $US 55 billion. Additionally, with over 25 000 known species, the biodiversity and ecological roles of fishes are being increasingly recognised in aquatic conservation, ecosystem management, restoration and aquatic environmental regulation. 2.,At the same time, substantial management problems now affect the production, exploitable stocks, global diversity, trophic structure, habitat quality and local composition of fish communities. 3.,In marine systems, key issues include the direct effects of exploitation on fish, habitats and other organisms, while habitat or water quality problems arise also from the atmospheric, terrestrial and coastal environments to which marine systems are linked. In freshwaters, flow regulation and obstruction by dams, fragmentation, catchment management, pollution, habitat alterations, exotic fish introductions and nursery-reared fish are widespread issues. 4.,Management responses to the problems of fish and fisheries include aquatic reserves in both marine and freshwater habitats, and their effectiveness is now being evaluated. Policies on marine exploitation increasingly emphasise fishes as integral components of aquatic ecosystems rather than individually exploitable stocks, but the rationalisation of fishing pressures presents many challenges. In Europe, North America and elsewhere, policies on freshwaters encourage habitat protection, integrated watershed management and restoration, but pressures on water resources will cause continued change. All these management approaches require development and evaluation, and will benefit from a perspective of ecological understanding with ecologists fully involved. 5.,Synthesis and applications. Although making a small contribution to the Journal of Applied Ecology in the past, leading work on aquatic problems and fish-related themes appear increasingly in this and other mainstream ecology journals. As this special profile of five papers shows, significant contributions arise on diverse issues that here include the benefit of aquatic reserves, river restoration for fish, the accumulation of contaminants, interactions with predators, and the fitness of salmonids from nurseries. This overview outlines the current context in which papers on the applied ecology of fish and fisheries are emerging, and it identifies scope for further contributions. [source]

Integrated catchment management in semiarid environments in the context of the European Water Framework Directive

LAND DEGRADATION AND DEVELOPMENT, Issue 4 2006
J. B. Thornes
Abstract Two recent developments draw attention to the need for integrated catchment management. First is the European Union's (EU) Water Framework Directive (WFD), which insists on an integrated catchment management plan for each European river basin within the next 15 years. Second is the current trend for river restoration; practitioners have concluded that this can only be achieved through a thorough appreciation of the integrated character of catchments. This paper addresses the question as to whether it makes sense to apply the WFD methodology across the range of European catchments and, in particular, what special provisions need to be made for dry Mediterranean catchments. The Southern European rivers are episodic. They yield high and coarse sediment loads and some are still used as waste repositories. They interact intermittently with groundwater. Reference conditions, both geometrical and water quality, require different measures and observations from those of the temperate and Arctic régime rivers that dominate much of the rest of the EU. These properties are identified and discussed with reference to nested subcatchments of the River Segura in the Province of Murcia, Spain. New research in the Nogalte sub-basin demonstrates a possible ,reference site' for this environment. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Towards an integrated environmental assessment for wetland and catchment management

THE GEOGRAPHICAL JOURNAL, Issue 2 2003
R Kerry Turner
This paper develops a decision support system for evaluation of wetland ecosystem management strategy and examines its, so far partial, application in a case study of an important complex coastal wetland known as the Norfolk and Suffolk Broads, in the east of England, UK. Most managed ecosystems are complex and often poorly understood hierarchically organized systems. Capturing the range of relevant impacts on natural and human systems under different management options will be a formidable challenge. Biodiversity has a hierarchical structure which ranges from the ecosystem and landscape level, through the community level and down to the population and genetic level. There is a need to develop methodologies for the practicable detection of ecosystem change, as well as the evaluation of different ecological functions. What is also required is a set of indicators (environmental, social and economic) which facilitate the detection of change in ecosystems suffering stress and shock and highlight possible drivers of the change process. A hierarchical classification of ecological indicators of sustainability would need to take into account existing interactions between different organization levels, from species to ecosystems. Effects of environmental stress are expressed in different ways at different levels of biological organization and effects at one level can be expected to impact other levels, often in unpredictable ways. The management strategy, evaluation methodologies and indicators adopted should also assess on sustainability grounds whether any given management option is supporting, or reducing, the diversity of functions which are providing stakeholders with the welfare benefits they require. [source]

Mixed stream channel morphologies: implications for fish community diversity

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009
Christina M. Cianfrani
Abstract 1.Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant. 2.Twenty-five stream reaches in north-western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool-riffle, mixed (i.e. pool-riffle/cascade, pool-riffle/other) and forced pool-riffle stream morphological groups. Stream reach surveys included cross-sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys. 3.Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon,Weaver Index (H,); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P,0.05), with pool-riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool-riffle the lowest. 4.These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool-riffle/cascade and pool-riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool-riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies. 5.These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional-distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Integrated river basin management in England and Wales: a policy perspective

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2002
G. Mance
Abstract 1.There is now an irresistible momentum for a truly integrated and strategic approach to river basin management. As a consequence, the framework within which individual organizations can carry out their roles and responsibilities in a co-ordinated and sustainable way can be determined. 2.Extreme events such as floods and droughts have severe social and economic consequences. ,Traditional' engineered responses, which take little account of fluvial processes and ecosystem functioning, often exacerbate these problems and can have severe adverse consequences on the environment. 3.Bringing together a range of scientific, technical and engineering disciplines to address catchment management has many advantages. Identifying and implementing innovative solutions that benefit local communities and the environment is the only sustainable way forward for river management. 4.Public understanding of risk assessment and management is vital to the success of an integrated approach. So too is a strategic dimension to inform the town and country planning system and major investment decisions by major utilities and public bodies responsible for water supply, pollution control and flood management. 5.There are major challenges ahead for public utilities, agencies and professional bodies in terms of attracting, retaining and blending together skilled scientific, engineering and technical specialists. These skills need to be complemented by the ability to convey sophisticated information in readily understood language. Copyright © 2002 John Wiley & Sons, Ltd. [source]