GROUNDWATER

1. Understanding of Groundwater

Groundwater is water that are on earth’s surface. Rain, dew, or snow, any of these (and many other) events—will causewater to end up on the surface of Earth. Once water is on the solid surface of Earth, it must do one of two things:

a)      Infiltrate.

The water that is made then seep into the ground. After the water is appear, it open to the earth surface until downer earth, from air-space in ground. It was also influenced by gravitational attraction.

b)      run off

Move across the surface to a lower elevation. By mean, the water do not seep into the ground but just there are on earth’s surface.  

Water also can evaporate, but if it doesn’t evaporate instantaneously upon its arrival at the surface, then it must infiltrate or run off first. Infiltration and runoff are each the result of gravity working to pull water drops closer to the center of Earth. This chapter will address infiltration and groundwater (water inside Earth). The following chapter will address runoff (water moving across the surface of Earth).

2. Infiltration.

            To infiltrate, individual water drops must move between the rocks and

rock particles to get below the surface. Several factors can influence the

proportion of water that will infiltrate or run off:

Slope of the Ground

Water that falls on flatter ground will be more likely to infiltrate than water that falls on steeper slopes.

Size of the Ground Particles

Water falling on bigger particles (with larger spaces between them) is more likely to infiltrate than water falling on little particles (with small spaces between them). Coarse sand and gravels have more infiltration because the space between the grains is large enough for water to easily pass through. Clay is comprised of very small particles and allows almost no water to pass.

Saturation of the Ground

If the ground already has water filling all the space between its particles, new water arriving at the surface will be unable to infiltrate and will run off instead.

Type and Intensity of Precipitation

A lot of rain falling all at once will promote runoff because only some of the newly arriving water will be able to get quickly into the ground. In contrast, the same amount of rain drizzling over several days might end up with nearly complete infiltration. If snow falls and very slowly melts, then nearly all of the water can infiltrate. If a lot of snow rapidly melts, that can produce a large amount of runoff (especially if it is raining as the snow melts).

Groundwater Movement

Gravity still will work on water, even after it infiltrates into the ground. Gravity pulls water very slowly through the ground. The water has to make its way through the spaces between all of the particles that make up the ground. Nevertheless, gravity always will be working to pull the water closer to the center of Earth. Sometimes there is an obstacle in the way of the water’s downward path. If the obstacle is an impenetrable barrier—solid rock, or a clay layer—then the water cannot move through it.

3.    Saturation and Water Table

The ground is said to be saturated if all the spaces between the ground particles are filled with water. The ground is holding as much water as it possibly can. There is an imaginary line that separates the saturated ground below the line from the unsaturated ground above that line. This line is called the water table. If a hole is dug into the ground and the hole goes deep enough to get below the water table, then the hole will fill with water. The ground below the water table is saturated—all the space between the ground particles is filled with water. It doesn’t matter how big the space is.

Sometimes holes are purposely dug below the water table so they will fill with water. A well is simply a hole in the ground that reaches below the water table—and then fills up. Water can be withdrawn by pumping or scooping it out of the hole. The water table marks the boundary between saturated and unsaturated ground. However, the position of the water table is not fixed. It can go up or down depending on how much water is being added or removed from the ground. If there is a net increase in the amount of water in the ground, then the water table will rise as more and more of the ground becomes saturated. Infiltrating water from rain, flooding, snow melt, or irrigation increases the amount of groundwater and raises the water table. In contrast, there can be a net decrease in the amount of groundwater if there is a decrease in infiltration. Infiltration can be reduced by drought. A change to the ground surface that acts to increase the amount of runoff instead of infiltration (e.g. building, paving, storm sewers) also will act to lower the water table. The water table also will be lowered if water is withdrawn from the ground at a well. If there is a drought or a very high rate of water withdrawal, the water table can drop below the level of a well, causing it to go dry.

4.    Run-off Water on the earth's surface.

The water on earth surface is a container of water contained in the earth's surface, not seep into ground. Form of surface water include rivers, lakes, swamps.

River

River is bargain water flow from natural source on the land. It surefire path to lakes, seas, oceans or other large rivers and the rain water or spring water that flows naturally through a valley or between two edges with clear boundaries, toward the lower.

River consists of three parts, are:

a)      Upstream, is located in an area that is relatively high so that water can flow down.

b)      The middle of the river lies in the more sloping areas.

c)      The lower reaches of rivers are located in areas already approaching ramps and river estuaries.

Lake

 The lake is located in the area of water collection basins in the earth's surface. Based on the occurrence, the lake is divided into:

a)      Drink water area lake, the lake formed as the river flows are naturally dammed by the lava flow eruption of the volcano.

b)      Volcanic lake, the lake formed due to volcanic eruptions, such as crater lakes Kelud, Batur and Galunggung.

c)      Tectonic lake, the lake formed due to fracture of the earth's crust caused by the activity of endogenous energy.

d)     Tectonic-volcanic lake, the lake formed due to a combination of tectonic and volcanic energy, such as Lake Toba.

e)      Karst lakes, lake area due to dissolution of the limestone surface of the limestone by rain water. Basin karst area called Dolina, Dolina and can be turned into a karst lake.

f)       Glacial lake / ice in ice area or glaciers.

Swamp

Swamp is lowland that alway flooded water that usually located in the area o sloping beach is general characteristic by mangroves or palm trees. There are many swamp areas of Sumatra's east coast, west and south coast of Borneo, west and south coast of Irian Jaya and the west coast of Cilacap (Central Java).

Gleyser

Geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase (steam).