2.6.1.6.1 Introduction

Section 2.6.1.6 summarises the prediction results for 30 surface hydrological receptors (see Table 4) and the eight hydrological response variables:

A ninth hydrological response variable defined in companion submethodology M06 (as listed in Table 1) for surface water modelling (Viney, 2016) – the annual number of zero-flow days (ZFD) – is not reported here because most of the streams in the Gloucester subregion are perennial (see Section 2.6.1.4).

For each of these hydrological response variables a time series of annual values is constructed.

For each receptor, 10,000 sets of randomly selected parameter values were used to generate 10,000 replicates of development impact. From these, the best 1000 replicates for each hydrological response variable, as assessed by their ability to predict that hydrological response variable at the four observation sites, were chosen for further analysis. Each boxplot was generated from the resulting 1000 samples. The boxplots show the distributions over the 1000 replicates of the maximum raw change (amax) in each metric between the baseline and CRDP predictions, the corresponding maximum percent change (pmax) and the year of maximum change (tmax). In general, the most meaningful diagnostic for the flux-based metrics (P01, P99, AF and IQR) will be pmax, while the most meaningful diagnostic for the frequency-based metrics (LFD, LFS, LLFS and FD) will be amax.