To address the question, "If large quantities of domestic sewage are continuously emptied into a small stream, it leads to," we can break down the effects step by step.
### Step-by-Step Solution:
1. **Understanding Domestic Sewage**: Domestic sewage is wastewater generated from households, which contains various organic and inorganic substances, including nutrients, pathogens, and chemicals.
**Hint**: Think about what domestic sewage consists of and its potential impacts on the environment.
2. **Introduction of Sewage into the Stream**: When large quantities of domestic sewage are continuously discharged into a small stream, it increases the nutrient load in the water, particularly nitrogen and phosphorus.
**Hint**: Consider how the nutrients in sewage can affect the water quality and ecosystem.
3. **Eutrophication**: The increased nutrient levels can lead to a process called eutrophication. This is characterized by excessive growth of algae (algal blooms) due to the surplus of nutrients.
**Hint**: Reflect on what happens to aquatic plants and algae when there is an abundance of nutrients.
4. **Depletion of Oxygen**: As the algae die and decompose, the decomposition process consumes a significant amount of dissolved oxygen in the water. This can lead to hypoxic conditions (low oxygen levels), which are detrimental to aquatic life.
**Hint**: Think about the importance of oxygen for fish and other aquatic organisms.
5. **Impact on Aquatic Life**: The depletion of oxygen can result in the death of fish and other aquatic organisms, leading to a decline in biodiversity in the stream.
**Hint**: Consider the consequences for the food web and ecosystem balance when species die off.
6. **Water Quality Deterioration**: The overall water quality of the stream deteriorates, making it unsafe for human use, recreation, and wildlife.
**Hint**: Think about how water quality affects human activities and the health of ecosystems.
7. **Long-term Effects**: If the situation continues without intervention, the stream may become a dead zone, where few organisms can survive, leading to long-term ecological damage.
**Hint**: Consider the lasting impacts on the environment and the potential need for restoration efforts.
### Final Answer:
If large quantities of domestic sewage are continuously emptied into a small stream, it leads to eutrophication, depletion of oxygen, decline in aquatic life, deterioration of water quality, and potentially long-term ecological damage.
