How does sunlight cause water to flow in rivers

In addition, the metalimnion can fluctuate in thickness and depth due to weather conditions and seasonal changes The metalimnion is bordered on both top and bottom by an edge called the thermocline. The thermocline is defined as the plane of maximum temperature decrease In other words, when the water temperature begins to significantly drop, the thermocline has been crossed. As temperature and density are related, a second cline, known as a pycnocline exists at the same depths.

The pycnocline divides water column strata by density Below the second thermocline and pycnocline is the hypolimnion. This strata is usually too deep to be affected by wind, solar radiation and atmospheric heat exchanges The temperature of the hypolimnion is usually determined by the spring turnover.

This temperature may only change minimally, if at all, while stratified Lakes that completely mix at least once per year are known as holomictic lakes There are six types of holomictic lakes, with definitions based on average temperature and how frequently temperatures align These lakes and their dividing factors can be seen in this flow diagram:.

Lakes that do not mix completely are called meromictic lakes These lakes have a lower strata that remains isolated throughout the year. This bottom layer is known as the monimolimnion, and is usually divided from the collective layers above it mixolimnion by a halocline salinity-based cline Meromictic conditions can occur in a holomictic lake when unusual weather conditions cause the lake to stratify before it has time to completely mix Pressure does not directly alter water temperature.

Instead, it shifts the freezing, boiling and maximum density points. The temperature at which boiling and freezing occur will only hold true at sea level 3. This is due to the effect of atmospheric pressure. At a lower pressure higher altitude , water will boil at a lower temperature. On the other side of the scale, at higher pressures such as in a pressure cooker , water will boil at a higher temperature Atmospheric pressure does not affect the temperature of the water itself, but only its ability to become vapor, thus shifting the boiling to the left or right.

As the hydrostatic pressure increases, the freezing point lowers At high elevations lower pressure , there is a slight increase in the freezing point, but the change in pressure is not enough to significantly affect the point Water temperature can be affected by many ambient conditions.

Shallow and surface waters are more easily influenced by these factors than deep water The greatest source of heat transfer to water temperature is from sunlight Sunlight, or solar radiation, is a form of thermal energy The result is a daily fluctuation in water temperature based on the amount of sunlight received by the water. If a body of water is deep enough to stratify, sunlight will only transfer heat through the photic zone light-reaching.

Most of this energy greater than half is absorbed in the first 2 m of the water This energy will continue to be absorbed exponentially until the light is gone. The photic zone varies in depth but can be up to m deep in the oceans The depth of the photic zone is based on the amount of solids and other light-scattering elements present in the water. The temperature of water below the photic zone is generally only altered when the water is mixed Thus shallower bodies of water tend to warm quicker and reach higher temperatures than deeper water bodies 1.

As heat always flows from a higher temperature to a lower temperature, this transfer can go both ways 6. When the air is cold, warm water will transfer energy to the air and cool off. If the air is hot, cold water will receive the energy and warm up. The extent of this transfer is based on the thermal inertia and specific heat of water Water temperature fluctuations are more gradual than air temperature fluctuations Increased turbidity will also increase water temperature.

Turbidity is the amount of suspended solids in water. These suspended particles absorb heat from solar radiation more efficiently than water The heat is then transferred from the particles to water molecules, increasing the temperature of the surrounding water Groundwater, streams and rivers can alter the temperature of the body of water into which they flow.

If a spring or groundwater source is colder than the river it flows into, the river will become cooler. Recalling the rules of heat transfer energy flows from hot to cold , the river loses energy to the cooler water as it warms it up 6. If the inflow is large or fast enough, the equilibrium temperature of the water will be close to the temperature of the inflow 1.

Glacial fed streams will keep conjoining rivers cooler near the source of the flow than further downstream 1. Man-made influences on water temperature include thermal pollution, runoff, deforestation and impoundments.

Thermal Pollution Thermal pollution is any discharge that will dramatically alter the temperature of a natural water source This pollution commonly comes from municipal or industrial effluents 1. If the temperature of discharge is significantly warmer than the natural water, it can negatively affect water quality. There are several significant consequences of thermal pollution, including diminished dissolved oxygen levels, fish kills and influxes of invasive species Runoff from parking lots and other impervious surfaces are another form of thermal pollution.

Water that flows off of these surfaces absorb much of their heat and transfer it to a nearby stream or river, elevating the temperature 9. Rising air currents take the vapor up into the atmosphere, along with water from evapotranspiration , which is water transpired from plants and evaporated from the soil.

The vapor rises into the air where cooler temperatures cause it to condense into clouds. Air currents move clouds around the globe, cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years.

Snowpacks in warmer climates often thaw and melt when spring arrives, and the melted water flows overland as snowmelt. Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans.

Runoff, and groundwater seepage, accumulate and are stored as freshwater in lakes. Not all runoff flows into rivers, though. Much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers saturated subsurface rock , which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies and the ocean as groundwater discharge , and some groundwater finds openings in the land surface and emerges as freshwater springs.

Over time, though, all of this water keeps moving, some to reenter the ocean, where the water cycle "ends" For an estimated explanation of where Earth's water exists, look at the chart below. By now, you know that the water cycle describes the movement of Earth's water, so realize that the chart and table below represent the presence of Earth's water at a single point in time. If you check back in a thousand or million years, no doubt these numbers will be different! Notice how of the world's total water supply of about million cubic miles 1, million cubic kilometers of water, over 96 percent is saline.

And, of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Thus, rivers and lakes that supply surface water for human uses only constitute about 22, cubic miles 93, cubic kilometers , which is about 0.

One estimate of global water distribution Percents are rounded, so will not add to The air is full of water, even if you can't see it. Higher in the sky where it is colder than at the land surface, invisible water vapor condenses into tiny liquid water droplets—clouds.

When the cloud droplets combine to form heavier cloud drops which can no longer "float" in the surrounding air, it can start to rain, snow, and hail What is streamflow? How do streams get their water? To learn about streamflow and its role in the water cycle, continue reading.

Metal s like copper are good conductors for electricity in homes and businesses. Clothes, carpets, and human beings can be conductors of static electricity currents. The strength of electricity is measured in ampere s amps. The vacuum of space can actually be a conductor. The solar wind is a flow of a type of electricity from the sun. The solar wind flows all the way to the edge of the solar system.

On Earth, the solar wind is blocked by the atmosphere. We can see the impact of the solar wind as the Northern Lights and the Southern Lights , bright slashes of color that sometimes appear in the sky near the North and South Pole s. Streaming Current Parts of the Gulf Stream ocean current are up to 80 kilometers 50 miles wide and more than a kilometer half mile deep. Abbreviated A or amp. The Coriolis effect makes storms swirl clockwise in the Southern hemisphere and counterclockwise in the Northern Hemisphere.

Mount Everest is part of the Himalaya and straddles the border of Nepal and China. The bright bands of color around the North Pole caused by the solar wind and the Earth's magnetic field. Also called a transmission line.

Also known as the aurora australis. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

The Rights Holder for media is the person or group credited. Caryl-Sue, National Geographic Society. Dunn, Margery G. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher.

They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource. If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media. Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website.

You cannot download interactives. Of that, only about 1. Most of our drinking water comes from rivers and streams. This water is the lifeline of ecosystems around the world. Ocean currents are the continuous, predictable, directional movement of seawater driven by gravity, wind Coriolis Effect , and water density.

Ocean water moves in two directions: horizontally and vertically. Horizontal movements are referred to as currents, while vertical changes are called upwellings or downwellings. Explore how ocean currents are interconnected with other systems with these resources. While sunlight is the energy source, the greatest force propelling the water cycle is gravity.

It pulls precipitation down from clouds and pulls water downhill. Gravity also moves air and ocean water. Cool, dry air is denser than warm, humid air, and cool, salty water is denser than warm, less salty water. Gravity pulls denser air and water downward, forcing less dense air and water to move upward. The warm water near the surface of the ocean heats up with sunlight and evaporates, keeping the water cycle in motion.