Water Resources: Definitions, Eutrophication, and Pollution
1. Key Definitions in Water Resources
a) Renewal Fee: The richness, diversity, and biodiversity of the environment.
b) Catchment Area: The area bounded by the union of all the headwaters that form the main river, or the territory drained by a single natural drainage system. In other words, it is the area that drains its waters into the sea through a single river or discharges them into a single lake. A watershed is bounded by a line of summits.
c) Water Table Aquifer: The aquifer is the level at which water runs in the subsoil. In the water cycle, part of the water is filtered and fed into the aquifer, also called the water table.
d) Ecological Flows: The minimum flow that should be maintained in an ongoing river after building a dam or derivation. This is done to avoid altering the conditions of the natural biotope and to ensure the development of river life, maintaining it as it existed previously.
e) Biological Oxygen Demand (BOD): A parameter that measures the quantity of matter capable of being consumed or oxidized by biological means in a liquid sample. It is used to determine the degree of pollution.
f) Sludge Line: Water purification extracts pollution from water, consuming energy and producing waste that concentrates all that was in the water. These products from the primary treatment are assimilated into solid urban waste. The sludge from the decantation undergoes special treatment until it can be treated as municipal solid waste, incinerated, or transformed into a product that, after other treatments such as stabilization or composting, can be reused as fertilizer in agriculture or for other uses.
g) Self-Purification: The process of recovery of a watercourse water after an episode of organic pollution. In this process, organic compounds are diluted and processed by biochemical breakdown, gradually increasing their stability.
h) Biological Contamination Indicator: Indicators of contamination by industrial waste are usually resistant to the total or partial absence of oxygen, low light, etc.
i) Saline Intrusion (Marine Intrusion): The process by which aquifers connected to the coast are invaded by seawater.
j) Pit: The surface area separating the basement flooded with groundwater in the area where cracks are filled with water and air.
k) Upwelling: A place where a reef, bedrock, or consolidated mineral layer in the subsoil appears on the Earth’s surface.
l) Consumptive Water Use: The use of water that is not returned immediately to the water cycle.
m) Non-Biodegradable Pollutants: Pollutants that do not break down or do so very slowly.
n) Water Cycle: The process of water movement between different compartments of the hydrosphere. This is a biogeochemical cycle with minimal intervention of chemical reactions, where water only moves from one place to another or changes its physical state.
2. Eutrophication: Process, Causes, and Affected Waters
Eutrophication is most observable in lakes. This process occurs when the water’s nutrient concentration rises, particularly nitrates and phosphates. Initially, a lake is in an oligotrophic state. Under these conditions, water transparency is high, and the vegetation at the bottom can perform photosynthesis, providing shelter and food for many animals. However, over time (possibly hundreds of years), lakes can transition into wetlands due to sediment accumulation and abundant plant remains. The lake eventually reaches a eutrophic state when nitrates and phosphates are released and concentrated, causing significant physical, chemical, and biological changes.
Eutrophication is a natural process, but it is accelerating due to the excessive use of inorganic fertilizers and phosphate detergents by humans, becoming a global problem.
Stages of Eutrophication:
- Phytoplankton Blooms Stage
- Aerobic Degradation of Organic Matter Stage
- Anaerobic Degradation of Organic Matter Stage
Effects of Inland Water Pollution:
- Loss of water quality, posing a risk to human health.
- Changes in aquatic ecosystem communities.
- Reduced recreational and aesthetic value of the environment.
3. Major Impacts on the Hydrosphere
a) Modification of Water Regime: The construction of dams and reservoirs transforms the river ecosystem into a lake ecosystem, resulting in numerous consequences. Sometimes, these impacts can pose risks to people.
b) Over-Exploitation:
- Over-exploitation of rivers
- Over-exploitation of aquifers
c) Pollution:
- Types: Physical, chemical, and biological.
- Water Quality: Water quality is defined by qualitative and quantitative parameters (physical, chemical, and biological) based on the intended use of the water.
- Contamination of fresh water
4. Physical Parameters to Detect Water Pollution
The physical parameters used to measure water quality are transparency (or its opposite, turbidity), color, smell and taste, electrical conductivity (indicating the amount of dissolved salt ions), temperature, and radioactivity.