Introduction: Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water.
97% of the water on the Earth is salt water. However, only three percent is fresh water; slightly over two thirds of this is frozen in glaciers and polar ice caps.The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air.
Fresh water is a renewable resource, yet the world's supply of clean, fresh water is steadily decreasing. Water demand already exceeds supply in many parts of the world[where?] and as the world population continues to rise, so too does the water demand. Awareness of the global importance of preserving water for ecosystem services has only recently emerged as, during the 20th century, more than half the world’s wetlands have been lost along with their valuable environmental services for Water Education. The framework for allocating water resources to water users (where such a framework exists) is known as water rights.
TYPES OF WATER RESOURCES: There are various types of water resources.
- Saltwater Resources: Saltwater is abundant in the world. However, saltwater is not useful when it comes to potable water supplies. Desalination plants, while they do exist, are scarce because the energy required for desalination makes the process extremely expensive. However, there are saltwater resources from which we benefit. Saltwater fish are a staple in much of the world's diet, but overfishing has put much of the fishing population at risk. Furthermore, tidal waters are being used as a source of hydroelectric energy. So, while saltwater is not helpful in dealing with scarce water supplies, it's inherent resources are being used.
- Groundwater Resources: Groundwater is the most plentiful of all freshwater resources. As water soaks into the ground, some of it adheres to clay and soil to provide water to the plants. This water is in the unsaturated, or vadose, zone. Most of the pores in the vadose zone are filled with air, rather than water. Gravity continues to move the water down through the ground. Eventually, the water reaches the saturated zone, where all the pores are filled with water. The separation between the saturated and unsaturated zone is called the water table.
Aquifers are areas of permeable rock that yield water. Aquifers are typically made of bedrock that has many fractures and connected pores, such as limestone, sandstone and gravel. Shale and clay layers are impermeable, and therefore make poor aquifers. An aquifer is recharged through precipitation. There is significant interaction between surface water and ground water. Groundwater feeds surface water through springs. Surface water can also recharge groundwater supply.
Groundwater is accessed by wells. A well is drilled down past the water table. A pump is placed in the bottom of the well, and it is pumped into homes, businesses and water treatment plants where it is dispersed. As water is pumped from the ground, a cone of depression forms around the well. The groundwater from the surrounding area moves towards the well. Wells can run dry during times of drought or if surrounding wells are pumping too much water, causing the cone of depression to be large.
3.Surface Water: Surface water is the water that exists in streams and lakes. This water is used for potable water supply, recreation, irrigation, industry, livestock, transportation and hydroelectric energy. Over 63 percent of the public water supply is withdrawn from surface water. Irrigation gets 58% of its water supply from surface water. Industry gets almost 98 percent of its water from surface water systems. Therefore, surface water conservation and quality is of utmost importance.
Uses of water:
- Due to its unique properties, water is of multiple uses for all living organisms.
- Water is absolutely essential for life.
- Most of the life processes take place in water contained in the body.
- Uptake of nutrients, their distribution in the body, regulation of temperature, and removal of wastes are all mediated through water.
- Human beings depend on water for almost every developmental activity.
- Water is used for drinking, irrigation, and transportation, washing and waste disposal for industries and used as a coolant for thermal power plants.
- Water shaped the earth's surface and regulates our climate.
Surface water: Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and sub-surface seepage.
Although the only natural input to any surface water system is precipitation within its watershed, the total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water loss.
Human activities can have a large and sometimes devastating impact on these factors. Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing stream flow.
The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a power plant that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when average stream flow is below the power plant's need.
Under river flow: Throughout the course of a river, the total volume of water transported downstream will often be a combination of the visible free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain called the hyporheic zone. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. The hyporheic zone often forms a dynamic interface between surface water and true ground-water receiving water from the ground water when aquifers are fully charged and contributing water to ground-water when ground waters are depleted. This is especially significant in karst areas where pot-holes and underground rivers are common.