Question

How could the irrigation of this farm field lead to the contamination of water supplies? Provide at least 2 specific examples.

(4 points)
grade 6

Answer 1

Here are two (actually four) specific ways irrigation can contaminate water supplies, with short explanations:

1. Fertilizer runoff and leaching
- When fields are irrigated, rain or irrigation water can wash fertilizers from the soil into nearby streams or lakes (runoff) or push dissolved fertilizer down through the soil into groundwater (leaching). This adds too many nutrients (like nitrates and phosphates) to water, which can make it unsafe to drink and cause algal blooms.

2. Pesticide/herbicide contamination
- Chemicals sprayed on crops can be carried by irrigation water into rivers, lakes, or wells. These chemicals can poison aquatic life and make the water unsafe for people and animals.

3. Soil erosion and sedimentation
- Strong irrigation or runoff can wash topsoil into waterways. The extra sediment makes the water cloudy, harms fish and plants, and can fill reservoirs and clog pipes.

4. Salinization and seawater intrusion
- Over-irrigation can raise the salt level in the soil; salty drainage can enter groundwater and surface water, making it unusable. In coastal areas, too much groundwater pumping for irrigation can pull seawater into aquifers, contaminating wells.

Any two of these examples would answer the question.