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            The earth and its ecosystems are largely affected by biogeochemical cycles, as discussed in Chapter 5. The hydrologic cycle, or water cycle, includes how water is evaporated into the air and precipitated back to the earth. One major component of this cycle that greatly affects mankind’s water resources is runoff, water that flows to large water basins during rain storms. This water can cause “serious nonpoint pollution” (Shan) to water sources it flows into by picking up chemicals and compounds from the topsoil and man-made structures it runs across. Many studies have been conducted to understand how this runoff loss can be reduced. “… The best method to prevent water quality degradation is to manage the domestic sewage, cropland, and woodland runoff.” (Qianqian) Preventing damage to water sources can be done by monitoring factors such as cropland runoff and creating methods to reduce pollution.

 

            In a study recently conducted in Chinese cabbage fields, large amounts of nitrogen from fertilizers were being fed into nearby lakes through runoff loss. The study stated that “A thorough understanding of [nitrogen] runoff losses is necessary for optimal [nitrogen] management in vegetable production systems.” (Shan) It is important to understand how runoff is being produced, and what components runoff possesses in order to maintain resources. This study found that different methods of fertilization created different amounts of nitrogen runoff. Conventional fertilization methods produced the most pollution, only causing runoff to lose about seven percent of nitrogen before reaching a nearby lake. However, slow-release fertilization methods caused runoff to lose over fifty percent of nitrogen before reaching the lake, decreasing the rate of degradation to the water quality. (Shan) By using different fertilization methods, farms are able to reduce pollution caused by runoff.

 

            Runoff is a significant factor in the hydrologic cycle, and it can negatively impact human water resources depending on the amount of chemicals it picks up. It is important to understand what conditions tend to create more pollution, and what simple changes people can make to avoid damage to resources. In this way, these resources can better be preserved and protected for a more sustainable usage that future generations can continue to rely on.