Birket or Birkat

This a term used in the eastern part of North Africa to describe a pond or a lake. They can be either fresh or Figure 6 Isli Lake (left) and Tislit Lake (right) - two substantial hard water lakes in the High Atlas Mountains (Morocco). Figure 7 North shore of Lake (Birket) Qarun (April 2003) - a salty lake at the margin of the hyper-arid Egyptian western desert. Note the absence of both vegetation and run-off drainage features on this shore. Figure 7 North shore of Lake (Birket) Qarun (April...

Further Reading

Hakanson L (1981) A Manual of Lake Morphometry. Berlin Springer. Hakanson L (2005) The importance of lake morphometry and catchment characteristics in limnology - Ranking based on statistical analyses. Hydrobiologia 541 117-137. Hutchinson GE (1957) A Treatise on Limnology Vol. 1). New York Wiley. Kotwicki V (1986) The Floods of Lake Eyre. Adelaide Engineering and Water Supply Department. Lowe DJ and Green JD (1987) Origins and development of the lakes. In Viner AB (ed.) Inland Waters of New...

Conservation Challenges

Although recognition of the looming freshwater crisis is growing, freshwater systems and their inhabitants are often still forgotten in local, national, regional, and international processes and plans. In part, this is due to the hidden nature of many freshwater species - they are literally 'out of sight and out of mind' underneath the water's surface. Additionally, many freshwater species are indistinct and small and thus do not engender the same emotional response as the large, colorful,...

Diversity

The proliferation and variation in the reservoir size, purpose for their construction and the hydrological Table 2 Physical and chemical characteristics of selected reservoirs of sub-Saharan Africa Table 2 Physical and chemical characteristics of selected reservoirs of sub-Saharan Africa Figure 7 The general topography of Africa showing the main watersheds, the areas over 1000 m, and the approximate division between High and Low Africa (Adapted from Beadle, 1981). Figure 7 The general...

Fisheries

Barbel (Barbus callensis, B. nasus, B. pallaryi, and Varicorhynus marocannus), Cobitis maroccana and, in the Nile fed lakes, an array of Tilapia species (T. nilotica and T. zillii) represent the main resident species in inland waters of North of the Sahara. These fish are found in a variety of habitats, including oasis and delta lakes. Fish aquaculture is frequently developed for mullet and for Tilapia in the Nile delta lakes. A few species are endemic to the region in the Nile system and...

Inland Lowland Lakes

Tropical lowland lakes As already mentioned, tropical South America is dominated by river systems. Thus, shallow fluvial lakes and lagoons associated with floodplains are the rule. In contrast to more populated regions of the world, the majority of South American floodplains retain most of their natural hydrological characteristics. These extensive floodplains are associated with the large rivers of the region. The running water of the rivers possesses considerable erosive power, which creates...

Institutional Development Contributions from the International Community4

The international community has long advocated the development of cooperative water management institutions for the world's international waterways, and has focused considerable attention in the 20th century on developing and refining principles of shared management. In 1911, the Institute of International Law published the Madrid Declaration on the International Regulation regarding the Use of International Watercourses for Purposes other than Navigation. The Madrid Declaration outlined...

Hydrology of Reservoirs

Among reservoirs, those built for generating hydro-electricity usually have the most pronounced fluctuations in water level (Figure 3). These fluctuations result from variations in the demand for electricity. Figure 3 Typical annual water-level fluctuations in boreal free-flowing rivers and in the two major types of impounded waters. Note that the range of fluctuations differs between water bodies and that the storage reservoir has reversed hydrological conditions during summer, with early...

Megene

Shallow Lakes Ecosystem

This term is used in the Maghreb countries for describing a small lake in mountain areas. A typical example is Megene Chitane in North Tunisia, a small, usually clear, soft water lake located on the north slope of Chitane Mountain at 150 m altitude, overlooking the Mediterranean Sea to the north. The site is protected and was declared a nature reserve in 1993. The outflow is ephemeral and maximum water depth is normally 1.2m. The catchment includes cork oak with fairly undisturbed scrub...

Lake Ellesmere a New Permanently Turbid State

Lake Ellesmere is a large (area 182 km2) but relatively shallow (2 m) lake on the east coast of South Island, New Zealand. Its waters were once clear and the lake had abundant aquatic weed beds that supported around 70000 black swans (Cygnus atratus). In April 1968, a powerful cyclone (the 'Wahine' storm) produced New Zealand's highest ever recorded wind speed (267 km h-1), and resulted in the drowning of 51 people when a boat sank between the North and South Islands and also decimated the weed...

Measures Taken to Reduce the External Loading

The key restoration target for all lakes is to reduce the external nutrient loading. Unless the loading has been reduced sufficiently to create a shift to a good ecological state in the long term, additional in-lake measures can only be considered as symptom treatments. Several simple empirical models have been developed to predict total phosphorus (TP) and total nitrogen (TN) concentrations in lakes on the basis of information on external TP and TN loading and between ecological state...

Productivity

In line with the low species diversity, the productivity of arctic lakes is generally classed as oligotrophic (unproductive) to ultra-oligotrophic. In unpolluted lakes the biomass of algae measured as chlorophyll a is often much less than 1 mg m 3 in the high arctic, and may increase to 3-5 mg m 3 in low arctic lakes just before or after ice-out. The rates of primary production in the water column can be variable but are equally low, typically from 1-200 mg Cm-3 day-1, and integrated annual...

The Rotorua Lakes

The shores of Lake Rotorua were a prominent site of battles between the Maori tribe Te Arawa and early European settlers. The European immigrants sought land from around the Rotorua lakes that was highly prized by Maori as a source of food and where many Maori settlements had developed. In 1922, the Crown advised Te Arawa Maori that because of the recession it was unable to afford a proposed settlement on sharing the lakes as a resource and instead offered to negotiate an annuity for 14 of the...

Summary

The dynamical interplay between stratification, waves, and wind can is best summed up in using the conceptual model proposed by J. Imberger in 1990 and supported by the more recent measurements by A. Wuest and others. A lake behaves like an engine that is powered by the wind and does work against the potential energy gradient embodied in the stratification. Approximately 2 of the wind energy flux 248 248.5 249 249.5 250 250.5 Time (day of year) 248 248.5 249 249.5 250 250.5 Time (day of year)...

Turbulent Energy Flux through the Water Column Synthesis

From the discussion above, we can draw the following overall scheme of the energy flux through the stratified waters of a lake. The origin of the energy for turbulent mixing is usually wind, which is imposing momentum onto the surface of the water. Approximately 3 of the wind energy from the atmosphere reaches the epilimnion in the form of horizontal currents and about 10 thereof is finally transferred to the stratified water body underneath. The major part of the energy is dissipated by bottom...

Functions of Reservoirs

Although all reservoirs are built to store water, their functions may differ. There are at least five major types of reservoirs but many are designed for multiple purposes. The management of multipurpose reservoirs builds upon compromises because it is nearly impossible to operate each function at its maximum level. This is the most common type of reservoir, built especially in dry parts of the world. Water in irrigation reservoirs is released into networks of canals 'Raw water' means surface...

Birds

Main migration routes are through Morocco, Tunisia, and eastern Egypt, and lakes on these routes are important habitats for these birds. Sites such as Merja Zerga, Ichkeul, Burrulus, Manzala are important resting areas for migrating birds. These wetland areas are inundated with migrant waders and waterfowl during each migration season and are supplemented by notable resident species such as the Coot (Fulica atra), Crested Coot (Fulica cristata), African Marsh Owl (Asio capensis), and...

Practical Guide to Measurement of these Waves

On the basis of the aforementioned disucssion, a step-by-step guide is provided on the method that should be applied when investigating these waves-Gravity Waves 1. Compute inertial frequency for the latitude of the lake in question using eqn. 1 . 2. Make a simple two-layer approximation to the stratification, and compute the equivalent water depth He using eqn. 4 . 3. Compute the internal wave speed using c VgHe. Typically this value will be between 0.1 and 0.3ms-1. 4. Compute the internal...

Geological History

Lakes can be seen as a mirror of the landscape that has been formed over thousands of years. The landscape of Europe is diverse, and major controls on this diversity are the north-south climatic gradient and geology. In the north, an ancient mass of crystalline rocks created a stable shield. This shield contains the oldest rocks of the European continent. During the Pleistocene epoch, large ice sheets formed that scoured and depressed the shield's surface. The entire landscape of the north has...

Classification of Ecosystem Services and Natural Capital

Ecosystem services are broken down into a number of categories. The Millennium Ecosystem Assessment listed four broad categories Provisioning services are those that provide goods such as food and water Regulating services are those that control various processes, such as flood control or suppression of disease outbreaks Supporting services, such as nutrient recycling, maintain material and energy balances and Cultural services are those that provide spiritual, moral, and aesthetic benefits. To...

Introduction

Mankind has used inland waters for transport, hunting and fisheries since the paleolithic times, as evident from archeological finds. Quarried neolithic stone masonry has probably been transported over water (Stonehenge megaliths, for example, came from 200 km westward), as it certainly has been during the last two millennia. For example, Roman occupation forces of the present Netherlands extensively used the river Rhine for transport and to patrol their boundaries. The Romans are also known to...

Plankton

Primary production in open waters is driven by phyto-plankton and many species have been described in the SMR since systematic research began earlier in the twentieth century (e.g., Gayral, 1954). The trend in availability of phytoplanktons related to the seasonal changes is comparable to that in European lakes with early and late summer peaks. However, high turbidity of some lakes can strongly depress phytoplankton growth despite an excess of nutrients. Green algae tend to be the most diverse...

Lake Manapouri New Zealand

Hydroelectric power was first generated from an underground station in Lake Manapouri in the Fiordland National Park of South Island, NZ, in 1969. Water discharged from the power station travels via two 10 km tunnels into a fiord on the Fiordland west coast. This station generates around 5400 GWh (billion Wh) of electricity annually, which is used almost exclusively for smelting aluminum at Tiwai Point on the southern coast of South Island. Original plans to raise the lake level by up to 30 m...

Zooplankton

Expansion of the water column provides changes in chemical characteristics that favor establishment of invertebrates. As reservoirs mature, there is generally an increase in the biomass of larval forms of terrestrial insects like Mansonia, mayfly nymphs, dragonfly, caddisfly, and truly aquatic insects like hemiptera and colleoptera, and mollusks. Crustacean zooplanktons colonize reservoirs according to feeding behavior filter feeders being first and predators are last. There are differences...

The Snowy River Scheme Australia

The Snowy Mountains scheme is the largest engineering project undertaken in Australia, beginning in 1949 and reaching completion in 1974. The scheme, in the High Country of Southern New South Wales, involved redirecting water from the east-flowing Snowy River through a series of tunnels and dams across the range to produce ten percent of New South Wales' power needs and deliver the water to the Murray and Murrumbidgee Rivers. The scheme has sixteen major dams, seven power stations and 225...

Climate

The arctic climate has high spatial variability, extreme conditions of solar radiation, and is characterized by both polar maritime and continental climates. Maritime conditions prevail over the Arctic Ocean, coastal Alaska, Iceland, northern Norway and adjoining parts of Russia, and result in cold winters and summer average temperatures of 10 C. Continental climates of the interior have more severe winters with lower precipitation, and while frost may occur year-round the average summer...

Legal Principles

The UN Convention on the Law of the Non-navigational Uses of International Watercourses (UN Convention), adopted in 1997 by the UN General Assembly, is one post-Rio accomplishment that specifically focuses on international transboundary water resources.7 The UN Convention codifies many of the principles deemed essential by the international community for the management of shared water resources, such as equitable and reasonable utilization of waters with specific attention to vital human needs...

Reservoirs for Hydro Power and Irrigation

Most artificial lakes used for generation of hydroelectric power or securing water for irrigation in Australia and NZ have been developed since the 1940s. Schemes of note in Australia include the Snowy River Scheme for hydroelectric power in the high country New South Wales, the hydroelectric network in Tasmania, the Hume and Dartmouth Dams in the headwaters of the Murray River, and the Ord River Scheme for controlling water release for irrigation requirements in Western Australia....

Reservoirs and Global Warming

Reservoirs play several roles in the ongoing global warming. One suggested role is advancing the increase of carbon emissions to the atmosphere, caused by the generation of greenhouse gases resulting from decomposition of impounded organic matter. However, given that some reservoirs are net C emitters and others not, the jury is still out on the total figure. Another role is masking the ongoing rise of ocean water levels following melting of inland ice, ground-water extraction, and the thermal...

Glossary

Bilharzia - A human disease caused by various species of trematode worms that use snails as an intermediate host also called schistosomiasis. Black flies - Insects in the family Simuliidae of the order Diptera some species are the vectors of the nematode worms that cause onchocerciasis. Buruli ulcer - A human disease caused by infection with the bacteria Mycobacterium ulcerans. Dengue fever - A human disease caused by a flavo-virus that is transmitted by infected mosquitoes. Dranunculiasis - A...

Issues in Ecosystem Service Assessment and Valuation

Ecosystem services are not always easy to quantify for a number of reasons. One reason is that information about a particular service, or the natural capital that generates it, may be imperfect or even completely lacking. For example, the benefits of aquatic ecosystems in developing countries may be unaccounted for because no research has been conducted on the scope and status of these systems. In developed nations, markets may distort the value of ecosystem goods and services, inflating or...

Lake Rehabilitation

If the problem with eutrophication is not solved pro-phylactically, i.e., by reducing the external nutrient input, it can be therapeutically approached by different rehabilitation methods, sometimes with good, but sometimes with less satisfactory results. Such rehabilitations involve physical removal of nutrient-rich sediment by dredging or chemically binding with e.g., ferric chloride or aluminium sulphate, or inactivating the phosphorus at the sediment and thereby considerably reducing the...

Lakes in the Alpine Region

Europe's most famous alpine lakes are located in the Alps. Lakes in the Alps are often associated with alpine lakes but when the term alpine is based on a biogeographical region division, true alpine lakes are here restricted to mountainous regions above the tree-line. Such alpine lakes are located at various altitudes in Europe, varying from the coastline in northern Norway to above 2000 m in the Alps. Lakes in the alpine region are usually headwater lakes (Figure 7), many of them without...

Artificial Lakes Drinking Supply Reservoirs

The population of Australia is highly concentrated in large coastal cities. Most Australian cities depend predominantly on drinking water reservoirs that capture and store surface water, although Perth in Western Australia uses about 40 groundwater for potable supply. Similarly, some larger cities in New Zealand are reliant upon small water supply reservoirs, despite large river systems, such as the Waikato River, being important potable water sources for major cities in New Zealand.

Formation Diversity and Distribution of Inland Waters North of the Sahara

North of the Sahara is defined as the southern Mediterranean region (SMR), an area surrounded by Atlantic Ocean in the west and Mediterranean Sea to the north. The SMR is located at the crossroads of three continents - Africa, Asia, and Europe - and displays much diversity in terrain, climate, and biodiversity. Both North Africa and the Middle East have considerable inland water resources with specialized aquatic flora and fauna. Internationally, many inland and costal lakes have particular...

Differences in Lake Restoration Strategies in Cold and Warm Climate Regions

Most lake restoration methods have been developed for temperate lakes and cannot be readily transferred to subtropical lakes and particularly not to tropical water bodies because they differ in many aspects from lakes in the temperate zone. For instance, in the Figure 8 Percent cover of aquatic macrophytes and chlorophyll a in Lake Conroe, Texas, before and after diploid grass carps were stocked in 1981-82 (33 fish ha-1). Modified from Cook GD etal. (2005), originally from Maceina MJ etal....

Land Water Interactions

Lakes everywhere are intimately tied to inputs of materials and nutrients from land, but this terrestrial connection is particularly strong in the Arctic for organic matter in dissolved and particulate forms. In terms of C (carbon), N, and P, the dissolved organic matter (DOM) concentrations typically represent 70-90 of the total C, N, and P in lake water or entering the lakes. This terrestrial connection is so strong mainly because the primary production of terrestrial environments is much...

Fish Fauna

The creation of lacustrine systems in artificial reservoirs provides a survival challenge to riverine species some of which fail to adapt, being unable to utilize organisms of the pelagic zone and to reproductive in new habitats. Clupeids have successfully occupied the pelagic zone and become the dominant group, whether through natural colonization as in Lake Volta or as introductions as in Lake Kariba and Cabora Bassa. Cichlidae have also been successful and so have Cyprinidae, Bagridae,...

Guelta or Galta or Gueltat

This term is used to indicate pockets of water left in drainage channels or wadis during the dry season the dimension and the duration of immersion vary from one guelta to another and from one region to another. They are temporary but can persist through very dry winters depending on runoff, water flow, and or groundwater. They can occupy meanders left by permanent rivers (cf. ox-bow lakes of north Europe) as well as in temporary wadis. In the arid and steppe areas, the gueltas occur in lowland...

Hydro Electric Developments on Large Rivers in New Zealand

The Waikato River (North Island), Waitaki and Clutha Rivers (South Island) have all been extensively dammed. The Waikato River begins at the outlet of Lake Taupo, the Waitaki River receives water from three main glacial-formed lakes where water levels are controlled, and the main inputs to the Clutha River also arise via glacial-formed lakes Wanaka, Wakitipu, and Hawea. Some statistics relating to these three hydroelectric dams are given below. Eight dams in series on the Waikato River, New...

Relevant Websites

Http www.dams.org - World Commission on Dams. http www.biodiv.org - Convention on Biodiversity (CBD). http www.earthtrends.org - Watersheds of the World, and Freshwater Resources 2005. http www.fishbase.org - FishBase. http www.gemswater.org - UNEP Global Environment Monitoring System (GEMS), Water. http www.giwa.net - Global International Waters Assessment (GIWA). http www.globalamphibians.org - Global Amphibian Assessment. http www.issg.org - Global Invasive Species Database. http...

Info

Primary producers -Phytoplankton Bacterioplankton Figure 5 Illustration of a typical lake food web including nine groups of organisms (phytoplankton, bacterioplankton, benthic algae, macrophytes, herbivorous zooplankton, predatory zooplankton, zoobenthos, prey fish and predatory fish). Calibration - Adjustment of variables within a model in order to achieve minimum bias. Effect-load-sensitivity model - A quantitative model that uses information on mass balance of nutrients or toxins to predict...

Impact of Changes in the Environmental Conditions on Density Currents and Deep Water Renewal

Changes in climatic conditions and human activities in catchments may affect density currents and thus vertical mixing in lakes. An increase in precipitation and in the percentage of the land made impervious by human development typically leads to a higher discharge of rivers. Enhanced river discharge is usually associated with increased erosion and a higher load of suspended particles in the river water such that density currents will propagate to larger depth. Enhanced deep-water renewal is...

Lakes in the Continental Region

The land use in the continental region in central Europe is dominated by agriculture and grassland, resulting in a high nutrient input into lakes. Consequently, many lakes are eutrophic (Figure 6). The continental region is relatively flat, giving raise to a variety of nutrient-rich shallow lakes. Shallow lakes have a special ecology because thermal stratification, influencing sediment-water interactions, is often lacking, making the lakes polymictic. Shallow lakes are frequently associated...

North America

Saline lakes are widely distributed throughout the western half of the North American continent where six regions can be distinguished including the Great Plains, the North West, the Great Basin, the Mid Continental Region, the Southwest Region, and the Chihuahuan region of North Mexico. One of the best studied is the Great Plains or Prairie Pothole Region. This area extends from the Dakotas and Western Minnesota into Southern Manitoba, Saskatchewan, and Alberta. No other area in the world has...

Insect Vectors of Human Disease

Biting flies (insects of the arthropod order Diptera) are the most important of the aquatic vectors of human disease. Of the flies, mosquitoes (the family Culicidae) are the most important vectors because of the high mortality and morbidity of the many diseases they transmit and because of the range of diseases for which they can serve as vectors (Table 1). For example, certain species of mosquitoes can transmit many Table 1 Examples of human diseases vectored by mosquitoes Disease vectored...

Jj

Where T is the period of rotation of the earth (1 day or 86 400 s), d is the latitude, and the units of f are radians per second. This parameter is zero at the equator (meaning that the effects of the earth's rotation on internal waves and currents can be ignored at the equator), and reaches a maximum value at the poles. The inertial period is defined as which is infinite at the equator, and has a minimum value of 12 h at the poles. We also define the Rossby

Conclusions

Although still in its infancy, the study of ecosystem services has brought out the tangible importance of aquatic systems to humanity. Much work remains, in terms of identifying the services, developing criteria for their measurement, and quantifying them. Nevertheless, it is clear that aquatic ecosystem services and goods provide billions and perhaps trillions of dollars' worth of benefit to societies. Historically, people often viewed Nature not only as a wily adversary, fraught with danger...

Seasonal Variability

The forcing functions of seasonal variations in lake chemistry fall into two categories. First is the concentration of salts, gases, and organic matter by evaporation in the summer or ice formation in the Figure 3 High-arctic Lake Hazen (left, 81.8 N) and low-arctic Toolik Lake (right, 68.38 N) showing the comparison of terrestrial vegetation in the catchment, leading to reduced inputs of organic matter from land into the high-arctic versus the low-arctic lake. (Photos left - W Vincent right -...

Geography and Geomorphology

South America covers an area of 17870218 km2 and spans a broad latitudinal range, extending from 12 28'N (Punta Gallinas, Colombia) to 55 59'S (Cabo de Hornos, Chile). Politically, the territory is divided into thirteen countries Colombia, Venezuela, Guyana, Suriname, French Guiana, Brazil, Ecuador, Peru, Bolivia, Paraguay, Uruguay, Argentina, and Chile (Figure 1(a)). At a regional scale, four major geo-morphologic regions may be identified 1. The Guaiana and Brazilian Highlands The Guiana and...

Amphibians and Reptiles

The turtle Mauremys leprosa is very common in different water bodies in North Africa but Emys orbicu-laris is very rare and limited to the Rif and the Atlas mountain areas. Dayas, Merja, and Aguelmane are important habitats for Bufo bufo spinosus, B. maur-itanicus, and B. viridis. Bufo bongersmai is more frequent in the desertic and arid areas (South west of Morocco and south of Algeria). Hyla meridionalis, Rana saharica, Discoglossus pictus, Alytes obstetri-cans, Pelobates varaldii are common...

Other Saline Lakes

There are many other saline lakes similarly affected by water diversions and threatened by secondary salinization. These include the Dead Sea, Lake Corangamite, Lake Balkhash, Pyramid and Walker Lakes, Qinghai Hu, and the Caspian Sea (Figure 6) Elevation of Lake Walker, for example, dropped 40 m from 1882 to 1996 and salinity increased from 2.6 to 12.4 g l_1 as a result of water diversion in the basin. This secondary salinization led to a decrease in tui chub minnow (Gila bicolor) numbers,...

Mono Lake

In 1941, the city of Los Angeles diverted water from the Owens River and three of four tributaries that fed Mono Lake in an effort to meet its increasing water demands. At the time Mono Lake was 2105 masl and salinity was 50000mg T1 (50 ). By 1982, however, lake levels had fallen to 2091 masl and salinity had almost doubled to 99 000mg l_1 (99 ) due to the water diversion. Shrinking water levels caused land-bridges to form between the mainland and islands, allowing coyotes and other predators'...

Natural Lakes and Their Spatial Distribution

For organizing the information about lakes and their distribution at the continental scale, we can divide the continent into several regions characterized by their landscapes with respect to lakes and their origins (Figure 2). These regions are essentially defined by their geologic histories, especially occurrence of glaciation and tectonic activity. Processes of lake formation vary from region to region for more complete discussion of lake origins refer to 'See also' section. Because these...

Major Ions

Tremendous numbers of coastal lakes and ponds in the Arctic are influenced by sea spray, particularly within 20-30 km of the coast. The ratios of major ions such as Na+, Cl3, and K+ in these lakes are similar to ratios found in seawater, with the exception that Ca2+ and HCO3 tend to be enriched over sea-water owing to inputs from weathering or most often from blowing soil (loess). Atmospheric inputs have little influence on the more inland lakes, however, which in all landscapes tend to be...

Species Diversity

For the most part lakes in the Arctic (1) are relatively depauperate with respect to biodiversity compared to temperate and tropical zones, (2) are populated mainly by cold adapted or cold tolerant species, and (3) have low productivity and simplified food webs. This relative impoverishment increases moving further north or to higher elevation, and it increases moving from lower to higher trophic levels in the food web (Table 1). That is, the ratio of arctic diversity to temperate or tropical...

Lakes and Reservoirs of North America

Lakes and reservoirs are found throughout North America. The combination of extensive glaciations and widespread dam building has resulted in a continent that is rich in lakes of all sizes, from the smallest features tens of meters across to the Great Lakes, which might be considered inland seas. In this article the terms 'lake' and 'reservoir' will be used to signify water bodies of natural and human origins, respectively, and this distinction is the primary framework for organizing the...

Habitats of Human Disease Vectors

Three important categories can be distinguished that provide habitat for vectors and intermediate stages of the causative agents of human diseases (1) natural water bodies (2) human-made water bodies, and (3) water bodies that form in human settlements and household environments. Freshwater vectors of human disease can occur in all of these habitat categories. In terms of natural water bodies, streams and rivers are sources of the black flies that serve as vectors of onchocerciasis, and lakes...

Effect of Salinity on Biodiversity

As salt concentration increases, however, biodiversity and species richness tends to decrease. At highest salinities, therefore, food webs become simplified. In highly saline Lake Nakuru, Kenya (TDS 10.0-120.0 g l_1), for example, the food web consists of a top predator (the lesser flamingo - Phoeniconaias minor), one cyanobacterial species (Oscillatoria spp.), two zooplankton species (one copepod and one rotifer) and one introduced fish species. Salinity in the Chany Lake complex of Siberia...

Conclusions and Future Research Needs

Currents in homogenous bodies and the upper mixed layers of stratified lakes are mainly the result of wind forcing applied at the free surface. The specific basin-scale patterns of motion that develop in response to wind depend on the specific spatial and temporal patterns characterizing the wind field (the frequency, intensity, duration, and location at the time of the events), interacting with the topography, internal waves, and Coriolis effects. By using a simplified and linear set of...

Examples of Ecosystem Services Generation in Aquatic Ecosystems

Wetlands have received a great deal of study over the past 40 years, and have become recognized as ecosystems having many valuable properties. As a result, many wetlands are now protected the world over, or if they are destroyed, replacement wetlands are created. Wetland ecosystem services include provisioning of food, freshwater, and building materials water filtration and purification critical habitat for many species of plants, amphibians, fish, and birds storm abatement, flood control, and...

Characteristic Geometry and Water Column Stratification

The internal waves described in this chapter are in lakes that are not affected by the Coriolis force due to the Earth's rotation for example, small lakes in the arctic, mid-sized lake (i.e., diameter > 5 km) in the mid latitudes, and large lakes near the equator. These lakes have a Burger number > 1. As we shall see later, the wave modes that are supported in such lakes depend upon the nature of the water column stratification. We limit the analysis to several characteristic types of...

Human Made Basins

Human activity has also played an important role in the development of lake basins all over the continent. Strip mining and road construction has produced a large number of artificial excavations. Once abandoned and flooded, these depressions form lakes. One example is Topibo Meer in Suriname, which is a large red-mud lake complex at an old mine site near Paranam. Nevertheless, the damming of streams and rivers has been, and continues to be, the most important human action responsible for the...

Willandra Lake and Aboriginal History

The Willandra Lakes is a World Heritage region and covers 2400 km2 of semi-arid landscape in far South-Western New South Wales. The region contains a system of Pleistocene lakes formed over the last two million years. The original source for the lakes was a creek that flowed from the Eastern Highlands to the Murray River but this has dried over the past several thousand years and become progressively more saline. Aborigines have lived on the shores of the Willandra Lakes for more than 60 000...

N P dC

In most limnological applications, density is used for stability considerations. Hence, density refers to potential density, i.e., the density of a certain water parcel under normal atmospheric conditions (1013 hPa). As a consequence of the (small) adia-batic compressibility of water, in situ density increases with pressure, i.e., water depth, by about 5 x 10-10 Pa. This means that at 200 m depth, (potential) density and in situ density differ by about 10-3. As direct...

Synthesis What Happens after a Biomanipulation

As stated in the introduction, the main theory behind biomanipulation is still focused on pelagic processes. However, both littoral and benthic factors, such as submerged macrophytes and benthic feeding fish, strongly affect the success of a biomanipulation, suggesting that these processes should receive equal consideration. Instead of being the only mechanism involved, alterations in the food chain may be viewed as triggers that initiate other processes. A biomanipulation has several 'primary...

Rf

Where c is the celerity (speed) of long gravity waves in the water body of interest, where we define long waves as those whose wavelength is far greater than the water depth. For surface ('barotropic') waves c y gH, where g is the gravitational constant (9.8 ms-2) and H is the water depth, as described in the preceding article. Note that it is possible to represent a stratified system as an equivalent depth of homogenous fluid so that the internal ('baroclinic') dynamics can be represented by...

Lake Physics

The physics of arctic lakes are controlled by the prevalence of ice and the extremes of solar radiation. Some high-latitude arctic lakes are permanently covered with ice up to 4 m thick, and nearly all are ice-covered for at least 8-11 months of the year. Even during the ice-free summer months average temperatures in surface waters rarely exceed 18 C and are more commonly less than 10 C. The bottom waters in some deep lakes stay cold year-round and may never reach 4 C, yet there exist lakes...

Threats to Ecosystem Services

Aquatic ecosystems and the services they generate are threatened by direct and indirect anthropogenic insults. These all-too-familiar threats include pollution, habitat loss and fragmentation, and overuse. The force of humanity over the past century has overwhelmed many aquatic ecosystems, or altered their functioning in ways that compromises delivery of ecosystem services. Some human alterations of aquatic systems have apparently opposite impacts. Dams and dikes obstruct the connectivity of...

Practicalities

In practice, biomanipulation can be performed either as an addition of piscivorous fish or as a removal of plank-tivorous fish, or by applying both measures simultaneously. Adding piscivores will, if successful, increase the predation pressure on planktivores, thereby allowing zooplankton to escape predation from planktivores and thus flourish and feed on phytoplankton, thereby increasing the clarity of the water. This method alone has, however, not proved to be very successful. The more common...

Acknowledgments

We thank Anne Mette Poulsen, Ramesh Gulati and Tinna Christensen for editorial and layout assistance. The study was supported by The Danish project CLEAR (a Villum Kann Rasmussen Centre of Excellence project), the EU EUROLIMPACS project (www. eurolimpacs.ucl.ac.uk), and the Finnish project CARE. See also Aquatic Ecosystem Services Benthic Invertebrate Fauna, Lakes and Reservoirs Biological-Physical Interactions Biomanipulation of Aquatic Ecosystems Lakes as Ecosystems Trophic Dynamics in...

W p

In this formulation, Kz describes the vertical transport of density caused by turbulent velocity fluctuations w' over a typical eddy distance L' given by the level of turbulence and the strength of the stratification. Therefore, in contrast to the molecular diffusion process, eddy diffusivity is neither a function of medium (water) nor of the water constituents (particulate or dissolved), but rather a property of the turbulent flow within the stratified water itself. In particular, Kz reflects...

Distribution

Just like natural lakes, big reservoirs occur close to main rivers. Figures 7 and 8 show the association between major reservoirs and key wetlands of sub-Saharan Africa. The biogeography of sub-Saharan fauna and flora shows patterns that can be reconstructed from the sequence of events which commenced with drifting apart of the continents. Within the sub-Saharan region, there are some keystone species that evidently connect water catchments. From the Nile to West Africa and southward to Zaire,...

Brief History of Reservoir Construction

Reservoirs - artificial water bodies created normally by construction of a dam across a stream, sometimes in combination with excavation of a depression - have been built in North America for hundreds and perhaps thousands of years. The Aztecs who built their city in the Valley of Mexico constructed dams to regulate water flows to the endorheic lakes of the valley. When Europeans occupied the continent in the 17th century they quickly began to build small dams that created ponds supplying power...

Food Web Manipulation

For fisheries enhancement purposes, nonnative species have been introduced into waters across the world. Subsequent consequences for food web composition were often unforeseen, as exemplified by the case of Lake Victoria. Here, introduction of the nile tilapia and nile perch brought species rich communities of native cichlid fish to extinction, but subsequent overfishing of these target species may well have led to recovery of some of these native species. In highly eutrophic lakes purposeful...

Africa

Saline lakes on the African continent are located in four major areas which include the northern half of the continent (Saharan and semiarid region bordering the Mediterranean), East Africa, the Western Rift Valley and South Africa. Perhaps the best known African lakes are the so-called soda lakes of East Africa. These sodium bicarbonate dominated lakes occur in a narrow strip extending from the Red Sea south through Ethiopia and Kenya into Central Tanzania and include small deep permanent...

Common European Lake Characteristics

To account for the most common characteristics of European lakes, a division of lakes according to their biogeographical region (Figure 4) has been implemented. This division might not be the most common one, but very appropriate for the entire Europe, since differences in climate, geological history, and land use are accounted for. Traditionally, lakes are classified according to their nutrient status. This kind of classification, where lakes are termed as oligotrohic, mesotrophic, and...

From Rights and Needs to Interests Baskets of Benefits

Traditionally, co-riparian countries have focused on water as a commodity to be divided - a zero-sum, rights-based approach. Precedents now exist for determining formulas that equitably allocate the benefits derived from water, not the water itself - a positive-sum, integrative approach. For example, as part of the 1961 Columbia River Treaty, the United States paid Canada for the benefits of flood control and Canada was granted rights to divert water between the Columbia and Kootenai for...

Merja

The term Merja indicates a shallow surface sheet of water with extensive mud flats. Deep mud is typical (1-2 m) and immersion can vary from daily, where there is tidal influence, to seasonal to permanent water. They are often brackish, high in suspended matter, but can be productive systems. The water level can exceed 4 m depth usually in March. The receding water level during summer leaves a large expanse of usually bare mud and salt deposits around the merja. The inundation limits vary not...

Garaet

In Tunisia, Garaet is a typical term for a large permanent body of water. An example for this is Garaet El Ichkeul, a large shallow brackish lake formerly famous for its water birds. It is surrounded by productive agriculture and major disturbances of its hydrological system occurred during the twentieth century. Following canalization, hydrological modifications were made to the five main inflowing rivers and all but one of these inflows has been dammed since 1984. Consequently, freshwater...

Vestfold Hills

Location The Vestfold Hills lie along the coast of Princess Elizabeth Land (68 25'-68 40' S, 77 50'-77 35' E) and occupy an area of 410 km2. The region and several outlying islands are typically snow free and contain 150 freshwater and saline lakes, which account for 8 and 2 of the total area, respectively. Formation and diversity Following the retreat of the continental ice sheet after the last glacial maximum 12 000 years ago, isostatic rebound occurred at a faster rate than sea level rise....

The Antarctic Continent An Overview of Lake Regions

Antarctica comprises more than 14x 106 km2, making it the fifth largest continent. Physically, it is divided into West Antarctica and East Antarctica by the Trans-antarctic Mountains. Antarctica is the coldest place on Earth with about 98 of the continent covered by permanent ice, which averages 2.5 km in thickness. The continent holds 70 of all the fresh water on Earth, in the form of ice. Average winter temperatures approach 75 C in the continental interior and 25 C along the margins. The...

Contaminants of Concern

The contaminants of most concern are nutrients and pathogens. The pathogens of most concern are Cryptosporidium, Giardia, Campylobacter, and viruses. The expansion of dairying and beef production in Figure 8 Lake Ellesmere, east coast of South Island, New Zealand. Note the Selwyn River inflow (left), the sand barrier separating the lake from the ocean to the east (top) and the encroachment of farmland to the lake edge (bottom), as well as the highly turbid nature of the lake. (Photo Alex...

Current Structure and Measurement

As we have made the linear wave assumption, the vertical velocities induced by these motions are small however, the horizontal current structure can show significant complexity both in the horizontal and vertical dimension. The complexity in the horizontal direction is due primarily to the presence of boundaries (and hence the horizontal structure of the waves), whereas the vertical complexity is due to both the stratification and the vertical mode. It is important to tie the vertical position...

Abundance and Size of Lakes Dictated by Climate and Geology

A global understanding of the role of lakes and impoundments in the functioning of any region of the Earth requires quantification of their number and size distribution. Geology, tectonics, and climatic processing have made the Earth's surface an undulating and tilted surface with a hypsometry defined by the amount of relief and the irregularity of the underlying materials. If this undulating surface is cut through by a plane (tilted or not) that represents the groundwater and surface-water...

Fish

Saline lakes, especially those with lower salt concentrations and ion species dominated by Na and Cl, can have complex food webs and be extremely productive. In fact some saline lakes support robust fisheries (e.g., Lake Issyk-kul, Caspian Sea, Lake Balkhash, Lake Chany complex, Siberia). Lake Issyk-kul, a large mesohaline (6000 mgl-1) sodium-sulphate-chloride lake in northeastern Kirghizia has 299 species of phytoplankton, 154 zooplankton species, 176 species of benthic invertebrates and 27...

Arctic Lake Ecosystems

Limnology is classically concerned with lake formation and geomorphology, and with lake physics, chemistry, and biology. Of the over 75 documented ways there are to form a lake, the Arctic contains examples of nearly all of those processes and certainly of lakes formed by the major categories of volcanic, glacial, and tectonic forces. But one unique aspect of arctic lakes is the role of thermokarst processes, which contribute to the most numerous lake forms on the planet. These shallow Figure 2...

Lake Chemistry

Arctic lakes exhibit a full range of chemistries, from very dilute waters with electrical conductivities approaching rainwater to waters concentrated by evaporation to beyond the salinity of seawater. Within this range, however, the majority of lakes are relatively dilute (conductivity < 300 mS cm-1) this is due in large part to the underlying permafrost, which isolates surface waters and soils from weathering interactions with deeper mineral soils and rocks. The unfrozen zone beneath lakes...

Size of Reservoirs

Lake Volta in western Africa is known as the largest human-made lake in the world - by area as well as by volume. It covers 8502 km2 or 3.6 of Ghana's area and has a maximum length of 520 km from its northernmost point at the town of Yapei downstream to the Akosombo dam. The volume of Lake Volta is 148 km3. When the reservoir was formed in 1965 about 78 000 people in 740 villages were relocated to new townships, along with 200 000 animals belonging to them. The reservoir is a major fishing area...

Effects of Climate Change on Lakes

W F Vincent, Laval University, Quebec City, QC, Canada 2009 Elsevier Inc. All rights reserved. Lake ecosystems are vital resources for aquatic wildlife and human needs, and any alteration of their environmental quality and water renewal rates has wide-ranging ecological and societal implications. The increasing accumulation of greenhouse gases in the atmosphere as a result of human activities has begun to affect the structure, functioning, and stability of lake ecosystems throughout the world,...

Paleolimnology

Due to their hydrologically closed nature, saline lakes are very responsive to past and present climate change. Paleolimnologists can track these climatic changes by examining cores from lake sediments. Preserved in the core are biological, geological and chemical signals - essentially clues which can reveal not only the ecological history of the lake but the surrounding landscape as well. Paleolimnological examination of cores from saline lakes, for example, has been used to predict the...

Aguelmane

The Berber term 'Aguelmane' or 'Aguelmam' is used only within the Middle Atlas of Morocco. It means a large, permanent, major natural body of water (often 6-40 m deep) and they are often surrounded by upland forest. Of all the North African water bodies, they are the nearest equivalent of a European upland lake. However, sometimes the term daya is also used to indicate this type of lake formation. Lakes are rare in the High Atlas Mountains but in the Middle Atlas Figure 5 Aguelmane Azigza...

Oases

Oases are characteristic of the hyperarid areas in or near desert areas. They are typically supplied by ground water or springs, and temporary rivers can also sustain some oases by conducting rainwater (above or below ground) from far away (e.g., the Nile and Draa rivers) to desert depressions. Where oases are fresh, aquatic vegetation and animal life can flourish. They are a foci for people, and human intervention for water use often disturbs standing water habitats in oases so that...

Lake Alexandrina and Lake Albert

There are two lakes at the terminal of the Murray Darling Basin, Lake Alexandrina and Lake Albert. Historically these lakes were estuarine and had complete connection to the Coorong and Murray Mouth. Barrages were built in 1940 to stop salt water incursion into the lakes and upstream into the River Murray during periods of low flow. The barrages drastically altered the ecology of the lakes which typically have been maintained at full pool level. As a result of a drought in 2006, and...

Nutrients

The total amounts of major nutrients (N and P) in lakes are usually set by the surrounding geology, rates of weathering, and geochemical reactions, but the observed concentrations of inorganic nutrients dissolved in lakes tend to be strongly controlled by biological processes. Arctic systems follow this generality as well, but what is special in these lakes is that the supply rates, geochemistry and biological controls are often at the extremes of typical behavior. Because of the isolation of...

The Arctic

The arctic region is defined geographically as lying above the Arctic Circle at 66 33'N latitude. However, similar to the distinction between montane (trees) and alpine (treeless) zones, the more typical definition of the arctic region is that it is treeless, which roughly corresponds to the 10 C July isotherm (Figure 1). A similar definition is that the arctic region is bounded by the southern limit of discontinuous permafrost (ground frozen for more than 2 years running). Whether the boundary...

Lake Ecosystem Ecology A Global Perspective

A DERIVATIVE OF ENCYCLOPEDIA OF INLAND WATERS PROFESSOR GENE E. LIKENS Cary Institute of Ecosystem Studies Millbrook, NY, USA Amsterdam Boston Heidelberg London New York Oxford Paris San Diego San Francisco Singapore Sydney Tokyo Academic Press is an imprint of Elsevier Academic Press is an imprint of Elsevier 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA 32 Jamestown Road, London, NW1 7BY, UK Radarweg 29, PO Box 211, 1000 AE...

Bird Habitat

Saline lakes around the world are important nesting, feeding and staging areas for all types of waterbirds. The saline soda lakes of east Africa are renowned habitats for pink flamingoes. Lakes Natron and Bahi, for example, have distinctively large populations of flamingos. According to a recent aerial survey, Lake Natron has the highest concentration of flamingos in East Africa. Both the greater and lesser flamingo (Phoenicopterus ruber and Phoeniconaias minor) are found at these lakes, with...

Functioning of Shallow Lakes and Ponds Biological Structure

The functioning of shallow water bodies is, as described above, strongly affected by the presence of aquatic plants and the fish structure. Aquatic plants exert multiple effects on the structure and functioning of shallow lakes and ponds. They affect the communities that live permanently or temporarily in the littoral area, through a series of physical, chemical and behaviorally-mediated processes. The structure of the fish community can, in turn, affect the lake functioning in contrasting ways...

Selected Examples

Table 2 provides an extensive list of examples of meromixis from many countries. The list is incomplete but gives a rich indication of this unusual lake type around the world. Other examples may be reported in the literature and, of course, many more probably remain unrecognized. Obviously, we need far more information and data but, based on current knowledge, it seems safe to say that less than 1 out of 1000 water bodies are known to have meromictic characteristics. However, even among the...