Which of the following is a potential negative impact of irrigation?

The selection of salt accumulation in surface water as a potential negative impact of irrigation is correct because irrigation practices can lead to the concentration of salts in the soil and water. When water is applied to crops and evaporates, the salts that were dissolved in the water are left behind, accumulating over time. This can lead to salinization of the soil, which negatively affects plant growth and agricultural productivity. As salts build up, they can contaminate nearby surface water sources, impacting the broader ecosystem and potentially harming aquatic life.

Increased soil moisture is generally seen as a positive outcome of irrigation, as it helps support crop growth. Enhanced biodiversity might also be interpreted as positive, as properly managed irrigation can create better growing conditions for a wider variety of plants and animals. Lastly, reduction of nutrient runoff is typically regarded as beneficial, as it implies that fertilizers are being used more efficiently without being washed away into water bodies. Thus, the nuances of irrigation practices reveal salt accumulation as a distinct and significant concern compared to the other options.