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regression models.

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    The relevance of flow regimes for both in-stream and out-of-stream values means that national representations of flow regimes may be used in national environmental reporting of New Zealand’s Freshwater state. This report describes: (1) Observed river flow time-series and river width used in this report. (2)Indices that may be of use in national environmental reporting to represent various parts of the flow regime: (a) the 1 in 5 year low flow (b) the 7-day mean annual low flow (c) the mean flow (d) the proportion of flow in February (e) the frequency of events exceeding three times the median flow (f) wetted river width at the 7-day mean annual low flow (3) Methods for calculation of these indices from flow time-series. (4) Regression models used to relate each index to known catchment characteristics. (5) Testing and validation of predicted values for each index. (6) National maps for each index when predicted onto New Zealand’s river network. (7) The format of data files containing the predicted and observed data (8) For wetted width, model performance was quantified by comparing predicted values with an independent data set. Model performance for ungauged sites was assessed by comparing observed values with out-of-bag predictions for the remaining hydrological indices. All models showed a good ability to discriminate between-site patterns.