Wetlands are being studied as a way to reduce pollution in rural areas. Researchers in Australia are measuring the water flow and chemical levels in three wetlands to see how they affect nutrient levels in run-off. They found that in winter, nutrients are released from the wetlands due to high flows, but in spring and summer, the wetlands retain nutrients despite similar water levels. The size of the wetland, the land use around it, and the type of vegetation all play a role in how effective the wetland is at trapping nutrients.