How do we calculate the discharge of a river using a catchment area?
Calculating the discharge of a river is complicated. It’s more complex than multiplying the area of the basin by the amount of precipitation. First there’s the time factor - if the precipitation falls as snow, it may be months before it leaves the basin. If it rains long enough the saturate the soils, how long will the river run high? Discharge volume changes over time, and lags behind precipitation. And that lag is never constant.Geology and soils play a big role in determining how much of rain and snow that falls in a basin actually exits, as well as how long it may take.Many upper basins serve as recharge zones for ground water aquifers. The water-holding strata are exposed or close to the surface in mountainous areas, and precipitation flows into the strata at these places. This becomes deep groundwater in nearby valleys - it never flows out of the drainage in a stream.The soils - depth, tilth, ratios of clay: sand: organic matter, and mineral composition - will also effect the time it takes for precipitation to percolate through and how much water will be retained for how long. Soil can hold a great deal of water.Evaporation removes some surface water from a basin before it has a chance to flow out as discharge. Many factors determine the volume and rate of water evaporated per acre or hectare: Number and type of plants, air temperatures, surface area of any ponds and lakes, wind speed, relative humidity, hours of sun, time of year.The best way to calculate discharge of a river is to measure it. This can be done accurately by setting up two ropes stretching across the stream, 5 meters apart. Measure and record distance shore to shore of each transect. Calculate average by adding the two width measurements and dividing by two. Then measure and record depth at regular intervals (eg. 1 foot) along each transect. Calculate average depth by adding up all the depth measurements and dividing by the total number of depth measurements. Convert units for average depth and average width to be consistent. Multiply to get square units. Use a stopwatch to measure seconds it takes for an item to float from first rope to second. Take several trials and find average flow rate. Multiply flow rate by square units and you get cubic flow per second. This is how it’s done in the field. It changes constantly.
How do humans influence the sulfur cycle?
Human activities influence the rates and character of certain aspects of the sulfur cycle in important ways, sometimes causing substantial environmental damages. Acid rain is a well-known environmental problem. Acid rain is ultimately associated with large emissions of sulfur dioxide to the atmosphere by human sources, such as oil- and coal-fired power plants, metal smelters, and the burning of fuel oil to heat homes. The SO2 is eventually oxidized in the atmosphere to sulfate, much of which is balanced by hydrogen ions, so the precipitation chemistry is acidic. In addition, the vicinity of large point-sources of SO2 emission is generally polluted by relatively large concentrations of this gas. If its concentration is large enough, the SO2 can cause toxicity to plants, which may be killed, resulting in severe ecological damages. In addition, atmospheric SO2 can be directly deposited to surfaces, especially moist soil, plant, or aquatic surfaces, since SO2 can readily dissolve in water. When this happens, the SO2 becomes oxidized to sulfate, generating acidity. This means a direct input of sulfur dioxide is called dry deposition, and is a fundamentally different process from the so-called wet deposition of sulfate and acidity with precipitation. Acid mine drainage is another severe environmental problem that is commonly associated with coal and metal mining, and sometimes with construction activities such as road building. In all of these cases, physical disturbance results in the exposure of large quantities of mineral sulfides to atmospheric oxygen. This causes the sulfides to be oxidized to sulfate, a process accompanied by the generation of large amounts of acidity. Surface waters exposed to acid mine drainage can become severely acidified, to a pH less than 3, resulting in severe biological damages and environmental degradation. http://science.jrank.org/pages/6600/Sulf...
What is the volume of water that sea levels have risen by?
Since 1900, sea levels have risen about 8 inches…0.2 meters.The surface area of the world’s oceans is 360,000,000 square kilometers - or 360,000,000,000,000 square meters.So the additional volume is 0.2 x 360,000,000,000,000 which is 72,000,000,000,000 cubic meters.(This is a slightly inaccurate estimate because as the water level rises, it inundates some land - so the surface area is slightly increasing as well as the depth).Where did all of that water come from?Well, the increase in the actual amount of ocean water comes from things like the melting of glaciers and runoff from the antarctic continent. (Note that the melting of things that float - icebergs, the antarctic ice shelves and the north pole - don’t contribute to sea level rise.)But that’s not the real reason for the problem.As we warm up the planet, the water expands. The average depth of the ocean is around 3,700 meters - so it only has to expand by the tiniest percentage to produce an 0.2 meter increase in depth.The scary thing is that air temperatures take a while to influence water temperatures at great depths - so we may push the air temperature up and not notice much effect on the oceans for a long time - but sooner or later, the ocean will rise in temperature by the same amount as the air - and then it’ll rise by a MUCH larger amount than you’d think by watching the present day sea level rise.