Time Series Statistical Analysis of Water Quality Model Results for the Rosetta Branch of the Nile River PDF

Keywords

Water quality modeling, time series analysis, statistical analysis.

Abstract

A physico-chemical water quality model has been developed and tested for the Rosetta Branch in the Nile Delta. Water quality models are tools for analysing, extrapolating and predicting the concentrations of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrogen in the form of ammonium (NH4-N) and nitrate (NO3-N), temperature (T) and total dissolved solids (TDS), taking into consideration advection, dispersion and the most important biological, chemical and physical processes. In this paper, the results of that model have been examined statistically based on the time series of hourly values of water quality parameters and discharges at km 125 along the Rosetta Brach. Relationships have been investigated between the water quality concentrations and loads and the river discharges. Theoretical distributions have been searched which best fit the time series for the different water quality parameters. They are applied to calculate exceedence probabilities for the thresholds involved in recommended water quality standards. The study concludes that, for DO, NO3-N and TDS parameters, average concentration values are within the recommended standard by law 481982/ (Egyptian standard). Moreover, the average concentration values for BOD and NH4-N violate the recommended standard. Also, the probability of exceedance of the recommended standard for BOD, NO3-N, NH4-N, DO and TDS concentrations are 72%, 15%, 99%, 9% and 19% respectively. Correlation analysis indicated that strong load-discharge relationships exist. The highest correlation coefficients for the load-discharge relationships were recorded for TDS and DO and the lowest correlation coefficient was recorded for NH4-N.