Carlson's Index is a Trophic State Index. It is used by the United States Environmental Protection Agency. The "trophic state" is the total weight of biomass in a given water body at the time of measurement. The Carlson index uses the algal biomass to classify a lake's trophic status.
Three variables are used to work out the Carlson Index: "chlorophyll pigments", "total phosphorus" and "Secchi depth". Chlorophyll is the most accurate measure, as it is the best predictor of biomass. Phosphorus may be better in summer. Secchi depth is the least accurate measure, but it is the cheapest and easiest to use. It measures how clear the water is. This shows how much dissolved and particulate material is in the water. This can be used to work out the biomass.
A lake can be put into one of three possible classes: "oligotrophic", "mesotrophic" or "eutrophic". Lakes with extreme trophic indices can also be called "hyperoligotrophic" or "hypereutrophic". Each trophic class has different types of fish and other organisms which live in them. If there is too much algal biomass in a lake or pond, then many fish can die as the decomposing biomass takes the oxygen from the water.
Oligotrophic lakes have very little or no aquatic vegetation and the water is clear. They have low levels of nutrients. The water is suitable as drinking water. The bottom waters of such lakes typically have lots of oxygen; thus, such lakes often support many fish species. Lake trout, for example, need cold, oxygen rich water. The oxygen content is likely to be higher in deep lakes, because of their larger amount of dense cold water.
Oligotrophic lakes are most common in cold areas. They are often on top of a layer of igneous rocks (especially granitic bedrock).
Mesotrophic lakes are lakes with a medium level of productivity. They usually have clear water with beds of submerged aquatic plants and medium levels of nutrients.
The term mesotrophic is also applied to terrestrial habitats. Mesotrophic soils have moderate nutrient levels.
Eutrophic lakes have large amounts of organisms, including algal blooms. They have a lot of nutrient and can support a lot of
aquatic plants and algae. Usually the water body will be dominated either by aquatic plants or algae. When there are a lot of aquatic plants the water tends to be clear. When there is a lot of algae the water tends to be darker. The process of photosynthesis in the algae supplies oxygen to the fish and plants which live these waters. Sometimes an excessive algae bloom will occur. This can kill fish by using all the oxygen in the water. The process of eutrophication can occur naturally and by human impact on the environment.
"Eutrophic" comes from the Greek "eutrophos" meaning "well-nourished", from "eu" meaning good and "trephein" meaning "to nourish"
Hypereutrophic lakes are very nutrient-rich lakes with frequent large algal blooms and low transparency. Hypereutrophic lakes have a visibility depth of less than three feet. They also have high levels of chlorophyll and phosphorus. The algal blooms can also reduce oxygen levels which can cause dead zones beneath the surface.
Both natural and human actions can decide a lake or other water body's Trophic Index. A lake in a nutrient-rich region may be
naturally eutrophic. Nutrients carried into water bodies, such as agricultural runoff, residential fertilisers, and sewage will all increase the algal biomass, and can easily cause an oligotrophic lake to become hypereutrophic.
Often, different people want different trophic states. For example duck hunters may want a lake to be eutrophic so that it will support large numbers of ducks. Residents, on the other hand, may want the same lake to be oligotrophic, as this is more pleasant for swimming and boating. Natural Resource agencies are generally responsible for managing the different demands and deciding what a lake's trophic index should be.
Ullswater
Ullswater is the second largest lake in the English Lake District. It is about nine miles (14.5 kilometres) long and 0.75 miles (1,200 m), wide with a maximum depth of slightly more than .
Many regard Ullswater as the most beautiful of the English lakes, it has been compared to Lake Lucerne in Switzerland.
It is a typical Lake District narrow "ribbon lake" formed after the last ice age when a glacier scooped out the valley floor. When the glacier retreated, the deepened section became a lake.Three separate glaciers formed the lake. The surrounding mountains give Ullswater the shape of a stretched 'Z' with three distinct segments (or 'reaches') that wend their way through the surrounding hills.
For much of its length Ullswater forms the border between the ancient counties of Cumberland and Westmorland.
The village of Glenridding, at the southern end of the lake, is popular with tourists of all kinds. For mountain walkers, England's third highest mountain, Helvellyn and other challenging peaks are near the lake. The village has ample accommodation including two Youth Hostels and camp sites. The village of Pooley Bridge is at the northern end of the lake. Its narrow 16th-century bridge straddles the River Eamont as it flows out of Ullswater; it is overlooked by Dunmallard Hill, which was the site of an Iron Age fort. On the western side of the lake is Aira force waterfall. Near there the Brackenrigg Inn overlooks sweeping views of the dramatic landscape.
Derwent Water
Derwent Water or Derwentwater is one of the main lakes in the Lake District National Park in north west England. It is in the Borough of Allerdale in the county of Cumbria.
The lake lies immediately south of the town of Keswick. It is both fed and drained by the River Derwent. It is about long by wide and is some deep. There are several islands in the lake, one of which is inhabited. Derwent Island House, an 18th-century residence, is a tenanted National Trust property open to the public on five days each year.
Derwentwater is very scenic. It is surrounded by hills (known locally as fells), and many of the slopes facing Derwentwater are wooded. A regular passenger launch operates on the lake, taking passengers between various landing stages. There are seven lakeside marinas, the most popular stops being: Keswick, Portinscale and the Lodore Falls, from which boats may be hired. Recreational walking is a major tourist activity in the area and there is a network of footpaths in the hills and woods surrounding the lake.
The Keswick—Borrowdale road runs along the eastern shore of the lake and carries a regular bus service. There is a lesser road along the western shore connecting the villages of Grange and Portinscale.
Derwentwater gave its name to the Earldom of Derwentwater.
The lake is believed to be the last remaining native habitat of the vendace ("Coregonus vandesius") fish.
Lake District National Park
The Lake District National Park is a National Park in North West England. It includes all of the central Lake District. The town of Kendal, some coastal areas, and the Lakeland Peninsulas are outside the park boundary.
The area was made a national park on 9 May 1951.
It is the most visited national park in the United Kingdom with 16.4 million visitors per year and more than 24 million visitor-days per year.
The Lake District is completely inside Cumbria, a county and administrative unit created in 1974 by the Local Government Act 1972.
All the land in England higher than above sea level lies within the National Park, including Scafell Pike, the highest mountain in England.
Ennerdale Water