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Interaction between surface water (stream) and ground water (aquifer) Surface water (streams) and ground water (aquifers) are interconnected in that one water source is used to recharge the other.Porous and permeable materials include soil (if not too clay rich), sand, sandstone, limestone, fractured igneous and metamorphic rock.Confining beds referred as Aquiclude, restrict the movement of ground water into and out of adjacent aquifers.aquifer , aquiclude and aquitard

Porous means having void spaces between grains.Aquifer: is a saturated permeable beds that will yield a usable quantity of water to a well or spring.Aquiclude: is confining bed which is relatively impermeable and does not yield usable quantities of water.The most productive aquifers, whether confined or unconfined, are generally in sand and gravel deposits.Impermeable materials include clay, shale, non-fractured igneous and metamorphic rocks.Porous/permeable layers are called aquifers; nearly impermeable layers called aquicludes.Porous/permeable layers are called aquifers; nearly impermeable layers called aquicludes.Diagrammatic sections showing influent and effluent streams.Rocks with large openings such as solution cavities or fractures can also be highly productive aquifers.During times of the year when the water table is high (mainly during rainy parts of the year), the ground water flows into the streams.This basic level of water is called baseflow (Figure 4a) and the stream is referred to as a gaining stream.Figure: Interaction between surface water (stream) and ground water (aquifer).Interaction between surface water (stream) and ground water (aquifer).Generally, the smaller the grain size or the less fracturing, the less water aquifer will produce.This is because there are fewer void spaces for holding water.During times of the year when the water table is low, the water in the stream flows into the ground water (Figure 4b).This type of stream is referred to as a losing stream. a) Gaining stream; b) Losing stream.Permeable means the voids are connected so water can pass through.Aquifer: Permeable to water flow.Aquiclude : Impermeable to water flow.Acts as a barrier (i.e. shale).Aquitard : intermediate condition.These tend to have large void spaces for holding water.Fig.

Interaction between surface water (stream) and ground water (aquifer)
Surface water (streams) and ground water (aquifers) are interconnected in that one water source is used to recharge the other. During times of the year when the water table is high (mainly during rainy parts of the year), the ground water flows into the streams.
This flow helps the streams maintain a basic water level. This basic level of water is called baseflow (Figure 4a) and the stream is referred to as a gaining stream.
During times of the year when the water table is low, the water in the stream flows into the ground water (Figure 4b). This type of stream is referred to as a losing stream.

Figure: Interaction between surface water (stream) and ground water (aquifer). a) Gaining stream; b) Losing stream.

Diagrammatic sections showing influent and effluent streams.

Ex. type of stream ?

Fig. Interaction between surface water (stream) and ground water (aquifer).

aquifer , aquiclude and aquitard

Porous means having void spaces between grains.
Permeable means the voids are connected so water can pass through.

Porous and permeable materials include soil (if not too clay rich), sand, sandstone, limestone, fractured igneous and metamorphic rock.
Impermeable materials include clay, shale, non-fractured igneous and metamorphic rocks.
Porous/permeable layers are called aquifers; nearly impermeable layers called aquicludes.
Aquifer: is a saturated permeable beds that will yield a usable quantity of water to a well or spring.
Aquiclude: is confining bed which is relatively impermeable and does not yield usable quantities of water.
Confining beds referred as Aquiclude, restrict the movement of ground water into and out of adjacent aquifers.
Porous/permeable layers are called aquifers; nearly impermeable layers called aquicludes.
Aquifer: Permeable to water flow.
Aquiclude : Impermeable to water flow. Acts as a barrier (i.e. shale).
Aquitard : intermediate condition.
The most productive aquifers, whether confined or unconfined, are generally in sand and gravel deposits. These tend to have large void spaces for holding water. Rocks with large openings such as solution cavities or fractures can also be highly productive aquifers.
Generally, the smaller the grain size or the less fracturing, the less water aquifer will produce. This is because there are fewer void spaces for holding water.

Types of aquifers

Aquifer - "A water-bearing layer of rock, or of unconsolidated sediments, that will yield water in a usable quantity to a well or spring." aquifers are often considered to be unconfined or confined.
Unconfined aquifer has no confining bed above it and is usually open to infiltration from the surface. A confined aquifer is overlain by a confining bed, such as an impermeable layer of clay or rock.

1. Unconfined aquifer:
   No confining aquiclude on top of aquifer. Usually is regional in extent. In an unconfined aquifer the zone of saturation (all voids filled with water) lies above an aquiclude; the top of the zone of saturation is the water table; aquifer is open to surface waters and are recharged through permeable soils and subsurface materials above the aquifer. Water is not under any pressure.
   
   Unconfined aquifers are often referred to as water-table aquifers and wells that are opened to these unconfined aquifers indicate the position of the water-table. Water freely rises and declines along the unsaturated/saturated zone boundary.

Perched aquifer:
Localized unconfined aquifer usually at a shallower depth than the regional aquifer. Caused by underlying aquiclude of limited extent. Quickly depleted and is more sensitive to local precipitation and pollution.
Perched aquifer occurs when an unconfined water zone has a clay lens, separated from the main aquifer below.

Technically speaking, Water table is the level at which the hydraulic pressure is equal to atmospheric pressure. Therefore, the water level found in unused wells is often the same level as the water table, as shown in Figure.

2.Confined aquifer or artesian aquifer:

Confined aquifer overlain by an aquitard or aquiclude. Water movement restricted to the sandwiched aquifer. Water usually under pressure due to its own weight (hydrostatic head). If drilled, water will rise to the potentiometric surface. This surface decreases in altitude with distance from the recharge area because of loss of ability due to friction.
Confined aquifers in complex geological formations may be exposed at the land surface and can be directly recharged from infiltrating precipitation.