what are surface waters
Surface waters are any body of water that exists above ground, including streams, rivers, lakes, wetlands, reservoirs, and creeks. Even though oceans consist of saltwater, they are also categorized as surface water. This water plays a crucial role in the hydrologic cycle, which describes the continuous movement of water between the Earth’s surface and the atmosphere. Precipitation and runoff contribute to the replenishment of surface water bodies, while evaporation and seepage into the ground lead to water loss. The water that seeps deep underground is classified as groundwater, highlighting the interconnectedness of these two vital water sources.
Types of Surface Water
Surface water can be divided into three main categories:
- Perennial Surface Water: This type of water is present year-round and includes lakes, rivers, and wetlands. Perennial bodies of water are sustained by groundwater, especially during periods of low precipitation.
- Ephemeral Surface Water: Also known as semi-permanent surface water, this includes bodies of water that exist only during specific times of the year. Examples include small creeks, lagoons, and seasonal waterholes.
- Artificial Surface Water: This category encompasses water bodies created by human intervention, such as dams, constructed wetlands, and artificial ponds. These man-made structures play important roles in water management and conservation.
The Importance of Surface Water
Surface water is essential for various human needs and ecological functions. It serves as a primary source of drinking water, irrigation for agriculture, and recreational activities. In the United States, approximately 80% of all water used in 2015 was sourced from surface water. Wetlands, which contain surface water, are critical habitats for diverse aquatic plants and wildlife, contributing to biodiversity and ecosystem health.
– Human Uses of Surface Water
Surface water is more accessible than groundwater, making it a preferred choice for many applications:
– Drinking Water: Communities rely heavily on surface water for their drinking supplies.
– Irrigation: Agriculture uses surface water extensively to irrigate crops, ensuring food security.
– Industrial Use: Various industries depend on surface water for manufacturing processes and cooling systems.
– Recreation: Lakes and rivers provide opportunities for recreation, including fishing, boating, and swimming.
Measurement of Surface Water
Monitoring surface water is crucial to understanding its availability and the impacts of human activities and climate change. Various methods and technologies are employed to measure surface water effectively:
– Annual Runoff Measurement
Surface water can be quantified through annual runoff, which considers the amount of rain and snowmelt that drains into water bodies after accounting for evaporation and transpiration from vegetation. For instance, the California Water Science Center utilizes a network of approximately 500 stream gauges to monitor surface water flow and annual runoff across the state. This data contributes to a national network overseen by the US Geological Survey (USGS), which maintains around 8,000 stream gauge stations.
– Remote Sensing Techniques
Remote sensing technologies, such as altimetry and interferometry, enable scientists to monitor surface water on a global scale. Altimetric missions, including TOPEX/Poseidon and the Jason-series, provide valuable data on major inland waters. However, traditional nadir altimetry has limitations, as it often misses over 60% of lakes, capturing only a fraction of global lake storage changes.
The Surface Water and Ocean Topography (SWOT) mission represents a significant advancement in this field. SWOT will offer high-resolution observations of nearly all surface water bodies, measuring approximately 65% of global lake and reservoir storage changes. This comprehensive view will allow hydrologists to calculate the rates of water gained or lost in lakes and reservoirs, as well as variations in river discharge.
Impacts of Climate Change on Surface Water
Climate change poses significant threats to surface water resources. As global temperatures rise, glaciers and sea ice are melting, leading to increased sea levels. This phenomenon allows saltwater from oceans to infiltrate freshwater aquifers, contaminating water supplies used for urban and agricultural purposes. Additionally, the stress on surrounding ecosystems affects wildlife habitats.
– Changes in the Water Cycle
Climate change directly influences the water cycle, resulting in increased evaporation and decreased precipitation, runoff, groundwater, and soil moisture. These changes can dramatically alter surface water levels. Furthermore, climate change exacerbates existing water quality challenges. The quality of surface water is influenced by chemical inputs from the surrounding environment; pollution from human activities can degrade water chemistry, impacting aquatic life and human health.
The Interrelationship Between Surface and Groundwater
Surface water and groundwater, while distinct entities, are interconnected components of the hydrologic system. The increasing demand for water necessitates effective management of both resources. Over-pumping of groundwater can lead to the depletion of surface water sources, particularly in aquifers located near river systems. Research indicates that excessive groundwater extraction can significantly impact surface water availability.
– Sustainable Management Practices
To ensure sustainable water supplies, management strategies must consider the interdependence of surface and groundwater. For instance, implementing restrictions on groundwater usage during periods of water scarcity can help maintain surface water levels necessary for aquatic ecosystems. By minimizing groundwater extraction, surface water resources can recharge through precipitation and runoff.
The Environmental Protection Agency (EPA) reports that approximately 68% of water supplied to communities in the United States comes from surface water. This statistic underscores the importance of preserving and managing surface water resources effectively.
Conclusion
Surface water is a vital component of the Earth’s hydrologic cycle, providing essential resources for human survival and ecological health. Understanding the types, importance, and measurement of surface water is crucial for effective management, especially in the face of climate change. As we strive to balance human needs with environmental sustainability, recognizing the interconnectedness of surface water and groundwater will be key to ensuring a secure water future for generations to come.
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Reference
1.Surface water
https://en.m.wikipedia.org/wiki/Surface_water
2.Surface Water
https://education.nationalgeographic.org/resource/surface-water/
