Water Harvesting: Importance and Techniques

Water harvesting refers to the collection and storage of water for future use. This practice is especially significant in regions where water scarcity is a concern, as it helps in ensuring a reliable water supply for agricultural, domestic, and industrial purposes. Below is an explanation of the importance of water harvesting and the techniques used in its practice.

Importance of Water Harvesting

1. Mitigation of Water Scarcity: Water scarcity is a major issue in many regions due to irregular rainfall, high population pressure, and increasing demand. Water harvesting provides an effective solution by storing excess water during the rainy season for use during dry spells. It reduces dependency on natural water bodies like rivers, lakes, and groundwater, which may be over-exploited.
2. Sustainable Water Use: Water harvesting ensures that water is available for agricultural irrigation, drinking, and industrial purposes, helping to sustain local ecosystems and reduce the exploitation of groundwater. It reduces water wastage and improves the efficiency of water use in agriculture.
3. Improvement of Soil Fertility: Collected water can be used to irrigate crops, especially in areas with low rainfall. Rainwater is typically low in salts compared to groundwater, making it beneficial for soil health and crop growth. When stored water is used during drought conditions, it can help prevent soil erosion by reducing the need for surface water diversion.
4. Reduction in Flood Risks: By capturing and storing rainwater, water harvesting can help reduce runoff during heavy rains. This decreases the likelihood of floods, which can cause damage to crops, infrastructure, and communities.
5. Enhanced Water Quality: Water harvesting, particularly when it involves filtering and storing rainwater, can improve the quality of water used for irrigation and drinking. Collected rainwater is often cleaner than surface water, especially if it is treated properly.
6. Support for Agriculture: In arid and semi-arid regions, where irrigation is a necessity for crop production, water harvesting provides a vital resource to ensure agricultural productivity and food security. It allows farmers to irrigate crops during dry periods, thereby enhancing crop yield and reducing the risk of crop failure.

Techniques of Water Harvesting

Several techniques of water harvesting have been developed to capture, store, and utilize water efficiently. These techniques vary according to the local climate, geography, and available resources. Some of the most commonly used water harvesting techniques include:

1. Rainwater Harvesting

Collection of Rainwater from rooftops, land surfaces, or paved areas is a simple and effective way to gather water for agricultural, domestic, or industrial use.

• • Rooftop Harvesting: Water is collected from the roof of a building and directed through pipes into storage tanks or ponds.
  • Surface Runoff Collection: Rainwater flowing over land is channeled into pits, ponds, or tanks for storage.

Components:

• • Catchment Area: The surface from which rainwater is collected.
  • Conveyance System: Gutters and downspouts to channel the water from the catchment area to the storage system.
  • Storage: Tanks, ponds, or other reservoirs where the water is stored for future use.
  • Filtration System: To ensure that the harvested water is clean and safe for use.

Advantages:

• • Simple and cost-effective.
  • Reduces the burden on groundwater resources and public water supplies.
  • Suitable for both urban and rural areas.

2. Surface Water Harvesting

Surface water harvesting involves collecting and storing water from rivers, lakes, or ponds, especially in areas where natural water resources are scarce or unreliable.

• • Check Dams: Small dams built across streams or rivers to capture and store rainwater during the rainy season.
  • Ponds: Excavated depressions in the ground designed to collect rainwater. Ponds can serve as both a water storage facility and habitat for wildlife.
  • Percolation Tanks: Large tanks or reservoirs designed to allow water to percolate into the ground, helping recharge groundwater levels.

Advantages: Large volumes of water can be collected and stored. Helps in groundwater recharge by allowing water to infiltrate and replenish aquifers. Useful for irrigation, especially in large-scale farming operations.

3. Check Dams and Small Reservoirs

• Check Dams are small barriers built across small streams or rivers to reduce the flow of water during rainy periods. The water is stored behind the dam and can be used for irrigation or drinking.
• Small Reservoirs or tanks are constructed to hold large volumes of water in catchment areas, which can then be used throughout the year.

Advantages:

• • Helps control water flow, preventing floods during heavy rainfall.
  • Provides an important source of water for communities, farms, and industries in water-scarce regions.
  • Reduces soil erosion by controlling runoff.

4. Infiltration Pits and Trenches

• Infiltration pits and trenches are excavated in the ground to capture rainwater and allow it to infiltrate into the soil, replenishing groundwater. Bore Wells and Infiltration Trenches can be strategically placed around agricultural fields to allow rainwater recharge into deeper soil layers.
• Advantages:
  • Helps recharge groundwater aquifers.
  • Minimizes water wastage and improves local water availability.
  • Suitable for areas with high evaporation rates where surface storage may not be feasible.

5. Farm Ponds and Tanks

• Farm ponds are small, dug-out basins that collect rainwater or runoff water for agricultural use. These ponds are typically designed to store water for irrigation during dry seasons.
• Water harvesting tanks or cisterns are used to store water at the farm level for irrigation. Tanks can range in size from small household-sized containers to large industrial tanks.
• Advantages:
  • Provides a localized source of water for small-scale farmers.
  • Reduces dependency on larger, centralized water systems.
  • Can be equipped with a drip irrigation system to reduce water loss and improve irrigation efficiency.

6. Contour and Terracing Water Harvesting

• Contour Bunding: Water is captured on the contours of sloped land, using bunds (embankments) to slow down water flow and prevent runoff. Water is allowed to infiltrate into the soil, enhancing groundwater recharge and reducing soil erosion.
• Terracing: Stepped levels are created on hilly land to capture and store water. Each terrace acts as a catchment, reducing water runoff and improving water retention.
• Advantages:
  • Highly effective in sloped or hilly terrain.
  • Helps reduce soil erosion and water loss.
  • Increases water availability for crops and enhances soil fertility.

7. Watershed Management

• Watershed management involves the management of water resources within a defined watershed or catchment area to optimize water use, prevent soil erosion, and ensure sustainable agricultural practices. It includes various techniques such as afforestation, soil conservation, and water diversion to increase water retention and reduce water runoff.
• Advantages:
  • Ensures long-term sustainability of water resources.
  • Improves overall land and water management.
  • Reduces soil erosion and enhances soil fertility.