Evaluation of the water quality at Tahtali dam watershed in Izmir-Turkey by means of statistical methodology

Abstract

Sustaining the human ecological benefits of surface water requires carefully planned strategies for reducing the cumulative risks posed by diverse human activities. Municipal governments in Izmir City play a key role in developing solutions to surface water management and protection. Therefore, several methodologies are carried out to develop new solutions for protecting available water resources. In the present study, the major chemical loads of surface water at the Tahtali dam reservoir were evaluated statistically by using monthly averaged values of the measured parameters. Here, the SPSS and NCSS statistical programs were applied during the statistical analyses. Analyses were carried out in two stages. In the first part of the statistical analyses, the mean, median, minimum, maximum, 25th and 75th quartiles were calculated. In second part, the data were investigated by using statistical median test, normality test, parametric and non-parametric correlation and regression analyses. These methods were performed on water quality data taken from four sample sites representing the recharge and discharge areas at the Tahtali dam. The Median test is applied to check if medians of water quality data from four sample sites (Derebogazi, Bulgurca, Menderes and Golcukler) are equal or not. Commonly a non-parametric test (distribution-free test) is used to compare two independent groups of sampled data. Since there are more than two groups in independent group comparison, Kruskal–Wallis test is applied instead of Mann–Whitney U test. Finally, the main objective of using statistical analyses in third research is to estimate the types of pollution sources, the level of pollution and its environmental impacts on the Tahtali dam reservoir by means of statistical methodology.