Ice and Snow.
Ice within the pore spaces of frozen soils typically reduces infiltration rates, but only soils that were saturated on freezing will completely prevent water from entering. Summer melting of the upper layer of permafrost in cold regions often results in a saturated zone of soil above the frozen ground.
Precipitation that falls as snow is stored until snowmelt, when a large pulse of runoff may be generated. Runoff occurs only after the entire snowpack has reached 0°C (32°F), some melting has occurred, and pore spaces between snow grains can no longer hold all the water supplied.
The rate of snowmelt depends on heat inputs into the snowpack through solar radiation and via water from melting and rainfall moving through the snow. The soil surface underneath the melting snowpack may become saturated, such that runoff flows through the base of the snowpack toward streams. Saturated zones and surface runoff commonly occur on slopes below the melting
snow line
.
Read more:
http://www.waterencyclopedia.com/Re-St/Runoff-Factors-Affecting.html#ixzz2DY8QkgXY
How This Year's Snowfall will Influence Next Year's Gardens and Farms
Many people understand that a water table has something to do with ground water, but they may not understand fully
what a water table entails or the purpose it serves
—and what weather elements cause the water table to fluctuate. In this blog, we'll break down water tables and explain how a nice winter of snow can actually ensure your gardens have plenty of water next year.
The "zone of saturation" is the underground depth at which the ground is totally saturated with water. The upper surface of this zone is called the water table. It is also the level at which groundwater pressure is equal to atmospheric pressure. Much of the water present on Earth is trapped under the ground. Rain, river and stream runoff and snow melt contribute to the water that seeps down into the soil and eventually into deposits of water under the ground. When water deposits are large enough to be used as a water source, they are known as aquifers.
The water table can fluctuate depending on the season and weather conditions. When there is an excess of rain or runoff, the water table may rise considerably. During periods of drought, the water table may diminish.
It's also important to note that a water table is not a flat line of water. The table actually fluctuates depending on the landscape and human modification of subterranean topography. The water table may be shallow in some areas and deep in others. In some cases, people may live in areas with a "high water table." The water may be enough to saturate the ground and contribute to springs where water flows naturally from rock onto the surface of the land. Springs may seep from places where the water table intersects the land surface. Water may also flow out of the ground along fractures. A high water table may contribute to leaks in basements and crawl spaces. That's because hydrostatic pressure, or the pressure of the groundwater pressing up against the home foundation, can cause the water to find weak points and other areas of entry. In these instances, a method of keeping the water from entering the home may need to be investigated.
Some people and industries tap the water table and aquifers for use. Underground water can provide irrigation for crops or be used to bring water to a home instead of relying on public water supplies. When a well is sunk to pump ground water, it must be put deep enough to reach the zone of saturation.
In areas with sufficient precipitation, water infiltrates through pore spaces in the soil, passing through the unsaturated zone. At increasing depths water fills in more of the pore spaces in the soils, until the zone of saturation is reached. In permeable or porous materials, such as sands and well fractured bedrock, the water table forms a relatively horizontal plane. Below the water table, in the
phreatic zone
, permeable units that yield groundwater are called
aquifers
. The ability of the
aquifer
to store
groundwater
is dependent on the primary and secondary
porosity
and
permeability
of the rock or soil. In less permeable soils, such as tight bedrock formations and historic lakebed deposits, the water table may be more difficult to define.
The water table should not be confused with the water level in a deeper well. If a deeper
aquifer
has a lower permeable unit that confines the upward flow, then the water level in a well screened in this aquifer may rise to a level that is greater or less than the elevation of the actual water table. The elevation of the water in this deeper well is dependent upon the pressure in the deeper aquifer and is referred to as the
potentiometric surface
, not the water table.
Snowfall
Generally speaking,
snow will raise the water table for longer than rain will
. Once the ground is saturated, rain will just continue to run off the surface, and no longer impact the local water table. However if in that same watershed, the precipitation falls as snow and it does not melt immediately then it will have a delayed impact on the water table, raising the water table later in the spring when the snow melts. In many seasonally arid mountainous places, the water table is dependent on snow melt through the dry season. So if that snow falls as rain, if temperatures rise, than those regions will not have the more continued water source that both the human and ecological communities depend on.
How does snow affect water supplies?
In the western United States, mountain snow pack contributes up to 75 percent of all year-round surface water supplies.
Snow that falls this winter will melt out of the ground in the spring, providing young plants with plenty of hydration.
What is the water content of snow?
The commonly used ten-to-one ratio of snowfall to water content is a myth for much of the United States. This ratio varies from as low as 100-to-one to as high as about three-to-one depending on the meteorological conditions associated with the snowfall.
Average snowfall amount
Nationwide, the average snowfall amount per day when snow falls is about two inches, but in some mountain areas of the West, an average of seven inches per snow day is observed.
Ice and Snow.
Ice within the pore spaces of frozen soils typically reduces infiltration rates, but only soils that were saturated on freezing will completely prevent water from entering. Summer melting of the upper layer of
permafrost
in cold regions often results in a saturated zone of soil above the frozen ground.
Precipitation that falls as snow is stored until snowmelt, when a large pulse of runoff may be generated. Runoff occurs only after the entire
snowpack
has reached 0°C (32°F), some melting has occurred, and pore spaces between snow grains can no longer hold all the water supplied.
The rate of snowmelt depends on heat inputs into the snowpack through solar radiation and via water from melting and rainfall moving through the snow. The soil surface underneath the melting snowpack may become saturated, such that runoff flows through the base of the snowpack toward streams. Saturated zones and surface runoff commonly occur on slopes below the melting
snow line
.
Read more:
http://www.waterencyclopedia.com/Re-St/Runoff-Factors-Affecting.html#ixzz2DY8QkgXY
How does snow affect water supplies?
In the western United States, mountain snow pack contributes up to 75 percent of all year-round surface water supplies.
What is the water content of snow?
The commonly used ten-to-one ratio of snowfall to water content is a myth for much of the United States. This ratio varies from as low as 100-to-one to as high as about three-to-one depending on the meteorological conditions associated with the snowfall.
Average snowfall amount.
Nationwide, the average snowfall amount per day when snow falls is about two inches, but in some mountain areas of the West, an average of seven inches per snow day is observed.
Ice and Snow.
Ice within the pore spaces of frozen soils typically reduces infiltration rates, but only soils that were saturated on freezing will completely prevent water from entering. Summer melting of the upper layer of
permafrost
in cold regions often results in a saturated zone of soil above the frozen ground.
Precipitation that falls as snow is stored until snowmelt, when a large pulse of runoff may be generated. Runoff occurs only after the entire
snowpack
has reached 0°C (32°F), some melting has occurred, and pore spaces between snow grains can no longer hold all the water supplied.
The rate of snowmelt depends on heat inputs into the snowpack through solar radiation and via water from melting and rainfall moving through the snow. The soil surface underneath the melting snowpack may become saturated, such that runoff flows through the base of the snowpack toward streams. Saturated zones and surface runoff commonly occur on slopes below the melting
snow line
.
Read more:
http://www.waterencyclopedia.com/Re-St/Runoff-Factors-Affecting.html#ixzz2DY8QkgXY
Ice and Snow.
Ice within the pore spaces of frozen soils typically reduces infiltration rates, but only soils that were saturated on freezing will completely prevent water from entering. Summer melting of the upper layer of
permafrost
in cold regions often results in a saturated zone of soil above the frozen ground.
Precipitation that falls as snow is stored until snowmelt, when a large pulse of runoff may be generated. Runoff occurs only after the entire
snowpack
has reached 0°C (32°F), some melting has occurred, and pore spaces between snow grains can no longer hold all the water supplied.
The rate of snowmelt depends on heat inputs into the snowpack through solar radiation and via water from melting and rainfall moving through the snow. The soil surface underneath the melting snowpack may become saturated, such that runoff flows through the base of the snowpack toward streams. Saturated zones and surface runoff commonly occur on slopes below the melting
snow line
.
Read more:
http://www.waterencyclopedia.com/Re-St/Runoff-Factors-Affecting.html#ixzz2DY8QkgXY
Winter Plants
Winter is the
hardest season for a plant's survival
; plants need water to live and in Winter the soil is often frozen with ice and snow, trapping any water within it. The plant can not replace any water losses and as a result, the plant will die. Therefore, plants and trees have adapted various ways in which to survive the Winter.
Which Plants Survive the Winter?
Annual plants do not the survive the Winter and flower for only one growing season; perennial plants do survive the Winter but 'hibernate' under ground. The growth above ground dies at the end of the growing season but the roots of the plant are protected by snow, which acts as insulation; new growth follows in the Spring.
How Snow Helps Winter Plant Survival
Snow is vital to the Winter survival of plants and trees as snow acts as an insulator and protects the plant from harsh, Winter conditions. Snow flakes have a unique structure; snow flakes have small intervening spaces within their structure which are filled with air. This means there is low heat conductivity; as a result, the daily temperature penetration into the snow is minimal and plants are protected from frost and freezing conditions. Once the snow melts, the moisture is also good for the plants.
Actually the old farmers prefer a snowy winter than a smooth winter season.
According to
the scientists, the connection between the cold and the earth is a
natural
one.
During the biggest snow storms, the vegetables in your
garden
will grow even healthier. Of course there are
advantages and disadvantages
, when it comes to
cold winters and veggie
gardens
.
The biggest amounts of snow aren’t that dangerous. They actually protect the vegetables against frost and ice, so the snow is providing a cover for your garden. For instance, snow is very useful for the flavor of many vegetables like Brussels sprouts and parsnips.
It improves their sweetness and makes them tastier. The snow has another major
advantage
, when it comes to healthy vegetables. If there is lot of snow, it kills the pest populations. Pest communities such as aphids can’t survive in low temperatures, so they will not damage your plants during a cold winter. It is a proven fact that the coldest winters are more useful for a veggie garden than a smooth winter.
Snow provides moisture as well as protection from cold and wind. Snow is an excellent insulator against low temperatures and excessive winds. The extent of protection depends on the depth of snow. Generally, the temperature below the snow increases by about 2 degrees F for each inch of accumulation. In addition, the soil gives off some heat so that the temperature at the soil surface can be much warmer than the air temperature. One study found that the soil surface temperature was 28 degrees F with a 9-inch snow depth and an air temperature of -14 F!
Snow brings welcome moisture to many landscape plants, which will in turn help prevent desiccation injury. Even dormant plants continue to lose moisture from twigs (as water vapor) in the process known as transpiration. Evergreen plants, which keep their leaves through the winter, are at even greater risk of injury.
The Effect of Changing Snowfalls on Plants
In some areas of the world snowfall is reducing; in other areas of the world snowfall is occurring earlier in the season than it has traditionally occurred. A
2007 UNEP report
Global Outlook for Snow and Ice stated that in the Northern Hemisphere snowfall had reduced by seven to ten per cent over the last 40 years for the months of March and April. Throughout the Northern Hemisphere, the period of the year when there is no snow cover has also lengthened.
If snowfalls occur early in the Winter season, or even at the end of Fall, some plants may traditionally be unprepared for the sudden climate change which may result in the plant dying; however, should snowfall be later or lighter in the traditional Winter months, plants may struggle to survive too. If high alpine and mountainous areas experience less snow, the traditional plant species found in these areas may eventually alter or die out completely.
When moisture from the sky falls short, it's our job to make up the difference with winter watering. When we go without a good soaking snow every month or so, we need to drag out our garden hoses and make up for the difference. Remember that on average, in our soil, 85% of a tree's roots are in the top 12- to 18-inches of soil. Trees, shrubs, perennials and even lawns don't need
frequent
winter watering, they need occasional
deep
winter watering. There's a big difference.
Newly-planted trees, shrubs and perennials need enough moisture to soak down to the bottom of their root ball. More mature plants will have larger root systems, and should be watered near their "drip line," the outer-most point of their branches.
