Water quality monitoring in the Xochimilco peri-urban wetland: experiences engaging in citizen science

Citizen science schemes for environmental monitoring generate benefits for scientists by increasing the capacity of scientists to gather information. Citizen scientist monitoring also benefits the citizens involved because they acquire a deeper knowledge and understanding of the benefits of ecosystems and the ways that anthropogenic activities affect them. This study details the efforts of a local non-government organization (Restauracion Ecologica y Desarrollo A. C.), the Earthwatch Institute, and the Hongkong and Shanghai Banking Corporation's Water Program to monitor the water quality in the Xochimilco peri-urban wetland, which is threatened by accelerated urbanization. The Xochimilco wetland includes agricultural areas in which raised beds called chinampas are surrounded by canals and small lakes. These chinampas have been managed for hundreds of years. The water in the canals is mainly used for agricultural irrigation, but it is also the habitat of a variety of aquatic species. In this study, we analyze the water quality of 7 canals and 1 lake located in areas with chinampas that have different uses such as housing, tourism, semi-intensive agriculture, agroecological farming, and abandoned agricultural land. Water samples from these sites were collected by citizen scientists over the course of 4 y. Our aim was to determine how the water quality varies across areas with management differences and between dry and rainy seasons. We found significant differences in pH, temperature, dissolved oxygen, Escherichia coli, and conductivity between seasons. We expected to find suitable water quality for irrigation (based on national and international guidelines) in canals near low-impact activities in the chinampas (such as agroecological farming or chinampas without human activities). Instead, we found that the water in those canals exceeded the recommendations for pH values (>9), total coliforms (>240 CFU/ 100 mL), conductivity (>2000 mu S/cm), and dissolved oxygen concentrations (<6.5 mg/L). However, nutrient concentrations were low. The structure of the canals near agroecological farming areas are narrow, shallow, and have low water flow, so alterations in the depth and width of these canals might result in improved water quality. The only sampling site that met most of the international and national guidelines for irrigation use was located in an area with many abandoned chinampas. Volunteers that participated in this study gained insights regarding the importance of being aware of anthropogenic impacts on ecosystems like the Xochimilco wetland, a place that is important to preserve because of its agricultural, ecological, and cultural significance.