A New Approach to Use Load Duration Curves to Evaluate Water Quality: A Study in the Doce River Basin, Brazil

Abstract

Although water availability depends both on qualitative and quantitative aspects, most studies focus only on one of these. Therefore, the goal here is to relate water quality and quantity with the construction of Load Duration Curves (LDC) and to estimate E. coli load patterns in different flow conditions, seasons, and positions of two sub-basins of the Doce watershed (Brazil): Piracicaba and Piranga. A novel methodology is proposed in which the Burr XII distribution is adjusted to the LDC to compare all observed loads to their respective Total Maximum Daily Load (TMDL), allowing the estimation of the relative difference (RD) between these. Higher values of RD were observed for low flows for the Piracicaba basin, more urbanized, where point sources of pollution are the primary concern, reaching up to 99% of needed load reduction. In the Piranga basin, more agricultural, there was a broader RD variation, from 9% to 97% load reduction needed, which is an evidence of point sources of pollution combined with non-point sources. The new methodology can be used to estimate the load reduction of any pollutant and can be used by environmental agencies to identify effective practices to minimize and control pollution in different locations of the basins.

Development of a Water Quality Index With a Reduced Number of Parameters

“…The methodology of calculation of the IGAM considers the premise that, in the absence of parameters E. coli or DO, one proceeds with the calculation of the WQI for a certain sampling point. In relation to the concentration of E. coli, this is probably due to the fact that this is a parameter of high concentration in the region of the study (Serrano et al 2020). The non-inclusion of E. coli in the reduced index could have jeopardised the good equivalence between the index as proposed and the index as currently practised, as the quality of the water in the Doce River basin was in many cases harmed, mostly due to the presence of E. coli, for having, on average, the lowest quantity (q = 20).…”

Analysis of the Water Quality Characteristics of Urban Streams Using the Flow–Pollutant Loading Relationship and a Load Duration Curve (LDC)

“…Chen et al conducted research on the application of the LDC method for the management of water pollution in the Yuanhe River, a tributary of the Ganjiang River, which itself is a tributary of the Yangtze River [14]. Serrano et al presented an alternative for estimating the coliform load reduction at various locations in the Piranga and Piracicaba basins using the LDC method [15]. As in the previous studies, LDC has been used in various ways to evaluate the water pollution load of rivers in space and time.…”