An analysis of the power promise and turmoil of north americas fresh water

Background[ change change source ] Coleridge, In SeptemberColeridge lived in Stowey and spent much of his time walking through the Quantocks with his fellow poet William Wordsworth and his sister Dorothy Wordsworth. Throughout the autumn, he worked on many poems, including "The Brook" and the tragedy Osorio.

An analysis of the power promise and turmoil of north americas fresh water

Resources The hydrologic cycle is the continuous circulation of water through the environment, which can be thought of as a series of hydrologic compartments. The most important places in which water occurs are the ocean, glaciers, underground aquifers, surface waters, and the atmosphere.

The total amount of water among all of these compartments is a fixed quantity. However, water moves readily among its various compartments through the processes of evaporation and transpiration often combined and referred to as evapotranspirationprecipitation, and surface and subsurface flows.

Each of these compartments receives inputs of water and has corresponding outputs, representing a flow-through system. If there are imbalances between inputs and outputs, there can be significant changes in the quantities stored locally or even globally.

An example of a local change is the drought that can occur in soil after a long period without replenishment by precipitation. An example of a global change in hydrology is the increasing mass of continental ice that occurs during glacial epochs, an event that can remove so much water from the oceanic compartment that sea level can decline by more than ft mexposing vast areas of continental shelf for the development of terrestrial ecosystems.

Major compartments and fluxes of the hydrologic cycle By far the largest quantity of water occurs in the deep lithosphere, which contains an estimated 27 x tons billion-billion tons of water, or The next largest compartment is the oceans, which contain 1.

Ice caps contain 0. Although present in comparatively small amounts, water in other compartments is important ecologically because it is present in places where biological processes occur.

These include shallow groundwater 2. The smallest compartments of water also tend to have the shortest turnover times, because their inputs and outputs are relatively large in comparison with the mass of water contained in the compartment at any time. This is especially true of atmospheric water, which receives annual inputs equivalent to 4.

These inputs of water to the atmosphere are balanced by outputs through precipitation of rain and snow, which deposit 3. The difference, equivalent to 0. The movement of water through the hydrologic cycle is driven by energy gradients. Evaporation occurs in response to the availability of thermal energy and water vapor concentration gradients.

The ultimate source of energy for almost all natural evaporation of water on Earth is solar electromagnetic radiation. This solar energy is absorbed by surfaces, increasing their heat content, and thereby providing a source of energy to drive evaporation.

In contrast, surface water and groundwater flow in response to gradients of potential energy.

An analysis of the power promise and turmoil of north americas fresh water

Hydrologic cycle of a watershed The hydrological cycle of a watershed is a balance between water added by precipitation and upstream drainage, and water removed by evapotranspiration, surface water flow, infiltration into the ground, and any internal storage that may occur because of imbalances of the inputs and outputs.

Hydrological budgets of landscapes are often studied on the spatial scale of watersheds, which are areas in which water flows into a stream, river, or lake.

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The simplest watersheds are headwater systems that do not receive any drainage from watersheds at higher altitude, so the only hydrologic input occurs mainly as precipitation. In places where fog is common, wind can drive droplets of water vapor into the forest canopy and the direct deposition of cloud water can also be important.

This effect has been measured for a foggy conifer forest in New Hampshirewhere fog water deposition was equivalent to 33 in 84 cm per year, compared with 71 in cm per year of rain and snow. Vegetation can have an important influence on the rate of evaporation of water from watersheds.

This hydrologic effect is especially notable for well-vegetated ecosystems such as forests, because an extensive surface area of foliage supports large rates of transpiration.

Evapotranspiration refers to the combined rates of transpiration from foliage, and evaporation from non-living surfaces such as moist soil or surface waters. Because transpiration is such an efficient means of evaporation, evapotranspiration from any well vegetated landscape occurs at much larger rates than from any equivalent area of nonliving surface.

In the absence of evapotranspiration an equivalent quantity of water would have to drain from the watershed as seepage to deep groundwater or as stream flow.

Forested watersheds in seasonal climates display large variations in their rates of evapotranspiration and stream flow.

An analysis of the power promise and turmoil of north americas fresh water

This effect can be illustrated by the seasonal patterns of hydrology for a forested watershed in eastern Canada. Although there is little seasonal variation in the input of water with precipitation, there are large seasonal differences in the rates of evapotranspiration, runoff, and storage of groundwater in the watershed.

Evapotranspiration occurs at its largest rates during the growing season of May to October, and runoff is therefore relatively sparse during this period.

In small watersheds in this region, forest streams can become seasonally dry because so much of the precipitation and soil water is utilized for evapotranspiration, mostly by trees. During the autumn, much of the precipitation input serves to recharge the depleted groundwater storage, and once this is accomplished stream flows increase again.

Runoff then decreases during winter, because most of the precipitation inputs occur as snow, which accumulates on the ground surface because of the prevailing sub-freezing temperatures. Runoff is largest during the early springtime, when warming temperatures cause the snowpack to melt during a short period of time, resulting in a pronounced flush of stream and river flow.

Influences of human activities on the hydrologic cycle Some aspects of the hydrologic cycle can be utilized by humans for a direct economic benefit. For example, the potential energy of water elevated above the surface of the oceans can be used to generate electricity.Latest breaking news from around the world, US, entertainment, science, technology, current events, politics and elections all on!

Analysis of the water-table aquifer adjacent to the Blackstone River in Massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer (negligible specific yield).

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