The ecological problems stem in large part from the fact that the brackish water and productive coastal wetlands and natural areas are often supplied with nutrient-rich irrigation return water, sometimes from rice farming. The Ebro Delta and its wetlands suffer similar water quality problems since they lie around the fringes of the large Delta farm region.

Based on that paragraph can we conclude that this sentence is true?
No problems arise from the irrigation water from rice farms flowing into nearby wetland ecosystems. 