Adopting basic quality tools and landscape analysis for applied limnology: an approach for freshwater reservoir management

摘要

Abstract Water quality degradation in reservoirs, as well as essential detailed analyses of limnological data and landscape analysis have gained much attention in recent decades. We implemented basic quality tools from the Plan–Do–Check–Act (PDCA) cycle to improve water management in the Barra Bonita Reservoir (Southwestern Brazil). These tools generated useful information concerning the causes of non-conformity of limnological variables with guideline values and the landscape pattern. We evaluated nine variables: biological oxygen demand (BOD5,20), dissolved oxygen (DO), pH, thermotolerant coliforms (FC), total phosphorus (TP), ammoniacal nitrogen (NH4), nitrate (NO3), nitrite (NO2), and turbidity (Turb). Three sampling stations were considered: two upstream (P1 and P2) and one downstream (P3). Limnological data (2007–2017) were obtained from sampling campaigns carried out in January, March, May, July, September and November of each year. Four quality tools were used: (i) Check List; (ii) Ishikawa Diagram; (iii) Pareto Diagram; and (iv) the Gravity–Urgency–Tendency (GUT) Matrix. As reported by the Check Sheet, the upstream rivers showed higher levels of non-conformity of limnological variables. The Pareto Chart showed that TP, DO, FC, and BOD5,20 correspond to 84.46 of non-conformities. According to the Ishikawa Diagram, and the Distance to Nature index (D2N), the water quality loss drivers correspond to sewage input (mainly from the Tietê river due to basic sanitation issues), non-point pollution, and intense anthropogenic land use. According to the GUT Matrix, the limnological variables of highest concern were the TP and FC, followed by BOD5,20. We explored the possibility of using quality tools to analyze reservoir data.