Analysis of existing water information for the applicability of water quality indices in the fluvial-littoral area of turia and Jucar Rivers, Valencia, Spain.

Abstract

For the first time, all the water quality information gathered by an European Union water district authority between 1990 and 2016 (the Spanish Jucar River Management Authority, Confederación Hidrográfica del Júcar, CHJ) was analysed and discussed. The main goal is to evaluate the applicability of this existing physicochemical information as potential data sources for continuous evaluation with Water Quality Indices (WQIs). Specifically, the spatial and temporal representativity of available data is assessed together with the applicability of WQIs both in time and space. A list of 42 existing WQIs with type and number of variables used was compiled after literature review. The study was carried out in the fluvial-littoral area of Turia and Jucar Rivers, Valencia, Spain, which was divided into six Landscape Functional Areas (LFAs), based on the outer continental perimeter zone, the irrigation areas of main channels crossing the flood plain, and the Albufera Lake. Input information consisted of a database, provided by the CHJ, of 67 sampling points with 401 physicochemical variables from 1990 to 2016, (about 283,023 records). This information was cross-analysed using descriptive statistics to evaluate the CHJ database information, the possibility of using WQIs, and the performance of target WQIs once their possible use both in time (27 years) and space (6 LFA) was established. Finally, a map representing the six LFAs was digitised, including the 67 sampling points and their water physicochemical characteristics. Results demonstrate that, out of 42 WQIs selected, seven can be used whenever all variables required are present. None of them can be calculated simultaneously at all stations and for all years. About 31% (21) of stations provided data that can be used in some years, and only 10% (27,430 values) of the database information is required for WQIs calculation. Indices that estimate repetitiveness (constant measure of water parameters over time) and consistency (coincidence of parameters measured at the 21 sampling points) show great disparity both in time and in parameters between sampling points. These results suggest that not only is it essential to obtain information on different compounds that may alter the water quality (to fulfil basin management authority policies), but also to establish a set of mandatory physicochemical parameters based on suitable application of some indices allowing temporary monitoring and comparison between them, in an accessible and repeatable manner.