In this article we are going to discuss about the construction of infiltration well with the help of appropriate diagrams.
Infiltration wells are Shallow wells constructed under the beds of rivers and canals. These wells are best suited for Indian conditions where there are deposits of sand and porous material a minimum of 3 mtr deep in river beds. In sand beds the water penetrates (Infiltrate) faster than clay (or) silty soil beds. As the water passes through the sand, which acts as filter, due to this all suspended organic and inorganic impurities will get removed.
So, the standards of such water is better than river water. Both infiltration wells and infiltration galleries are based on the same principle. A large number of wells are constructed in the river bed and they are connected to an inspection well. The water flows under gravity from these wells to the inspection well and then towards Jack-well from where it is pumped.
In order to obtain large quantity of water, infiltration wells are sunk in series in the bank of river. They are constructed of brick masonry with open joints. These are generally covered at top and kept open at bottom.
The various infiltration wells are connected by porous pipes to a sump well called Jack well. The water reacting the jack well from different infiltration well is lifted, treated and distributed to the consumers.
Purpose of construction of Infiltration wells:
• Preserving and improving the quality and quantity of ground water.
• To help cope with water shortages.
• Cultivating environmental awareness.
• Conserve and save water resources long term.
Factors to Consider in Making the well of Infiltration:
(i) Topography:
The valley regions are more favorable than the slopes and the hilltops.
(ii) Climate:
The climate is a major factor to consider in planning the filtration wells. The region's annual rainfall, intensity of sunlight, maximum temperature and humidity are of considerable value. Areas having heavy (or) moderate rainfall favor more water to percolate in the soil and rocks layers, and get stored on impermeable layers to form aquifers.
Intensity of summer days evaporates and depletes ground water through direct evaporation from shallow depths and evapotranspiration through plants. Areas of low rainfall and extreme summer conditions do not favor storage of ground water at shallow depth and therefore the wells do not yield much water. Semi-arid zones are more favorable than the arid zones.
(iii) Vegetation:
Vegetation can flourish well where the ground water is available at shallow depths. The trees of forests draw their requirements directly from the 'Zone of Saturation'. Such plants are known as 'Phreatophytes'. Some plants can exist under arid conditions by absorbing the soil moisture (intermediate (or) vadose water) in the zone of aeration and store water in their thick fleshy leaves and stems. Such plants are known as 'Xerophytes'.
By studying the vegetation of the area, the condition of ground water can be assessed. This vegetation indicates large storage of ground water at shallow depths whereas bald hillocks with large number of Xerophytes indicate the scarcity of ground water at shallow depths.
(iv) Geology of the area:
Areas comprising thick soil (or) alluvium cover, highly weathered, fractured, jointed (or) sheared and porous rocks indicates good storage of groundwater, whereas bald hillocks of massive igneous and metamorphic rocks or impermeable shales indicate paucity of ground water.
(v) Porosity, permeability and Alteration of Rocks:
The state of the soil affects the size of the ground penetrating power of the rain. Thus highly porous, permeable and altered zones of dense rocks encourage storage of ground water. Massive rocks do not permit the water to sink. So while constructing infiltration wells we should take soil physical properties into consideration.
(vi) Socio-economic conditions of society:
Planning infiltration wells should pay attention to the social condition of the economy. For example, in a good economy, the cost of infiltration wells can be charged to the community and its construction can be made from a material that is really strong.
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