Water quality information system development : sample size optimization

Abstract EN

Sampling frequency is a very important consideration to control the efficiency of a water quality monitoring network.

A large portion of the costs of operating a monitoring network is related directly to the frequency of sampling applied to the water quality channels in the Nile delta.

The sampling frequency was carried out for the monitoring locations in Bahr Shebeen canal in Middle Nile Delta and Ismaillia canal in Eastern Nile Delta.

The statistical method of “Single Station, Single Variable” was used to assess and redesign of sampling frequency is based on the confidence interval around the mean value.

The approach helps identifying the sampling frequency that allows estimating the annual mean value with an acceptable accuracy.

Results indicate that the proposed approach represents a useful decision support tool for the optimized selection of water quality variables.

The results showed that 12 samples per year at the monitoring site of Bahr Shebeen canal may allow the estimation of the BOD and COD mean values with 27% and 25% error, respectively.

On the other hand, at the monitoring sites of Ismaillia canal may allow the estimation of the BOD and COD mean values with 45% and 50% error, respectively.