Quantifying the streamflow regime of Hanlon Creek, Ontario to develop streamflow management targets
Maintaining the natural hydrologic variability of streamflows is critical for conserving river ecosystems. The hydrological consequences of gradual urbanization between reference (1950s) and existing (2001) conditions in the Hanlon Creek watershed were investigated. The effects of stormwater management/recharge ponds and natural conservation areas on the streamflow regime were also considered. A calibrated hydrologic (GAWSER) model of the Hanlon Creek watershed was applied, using long term continuous rainfall data, to generate a daily streamflow time series at eight gauged and ungauged points of interests, under different land use scenarios. A flow assessment tool "Indicators of Hydrologic Alteration (IHA)" utilized in GAWSER and IHA software was demonstrated to characterize the natural and altered flow regime of the study area in terms of 34 ecologically related hydrologic parameters. The "Range of Variability Approach (RVA)" included in the flow assessment tool was also applied to assess the degree of flow alteration and to set initial river management targets to restore a near-natural flow regime. The study demonstrates the suitability of the suite of tools (GAWSER, IHA and RVA) for simulating daily flows; characterizing the flow regime (in terms of the magnitude, frequency, duration and timing of flows); quantifying the alteration of the flow regime due to urbanization; and setting flow targets for an urbanized watershed, based on a GAWSER generated daily streamflow time series. A methodology has been developed for applying and adapting these tools, which may be used in other watersheds.