Sydney
Water overview
Significant water events
Significantly lower rainfall combined with very much above average evapotranspiration across the region during the 2013–14 year (see Climate overview) has translated into reduced inflows (see Surface water inflows) and lower storage volumes (see Surface water assets) compared to the previous year. This has contributed to a reduction in overall surface water asset volume during the 2013–14 year.
Soil moisture
Figure W1 shows that soil moisture was generally average to below average in the Sydney region during the 2013–14 year (compared with the 1970–2014 period). It was very much below average or the lowest on record at several pockets in Coastal areas. The soil moisture is based on a simple conceptual representation of soil water storage and transfer processes averaged over a 5 km x 5 km grid cell derived from the Australian Water Resources Assessment system landscape model (AWRA-L) version 3.0. The model produces a soil moisture grid for the region at a daily time step, which is then averaged over the entire year to produce an annual soil moisture grid. The annual grid represents the mean daily volume of soil moisture across the region during the year.
Figure W1 Annual soil moisture deciles for the Sydney region during the 2013–14 year
As shown in Figure W1, soil moisture for the region was generally average or below average. It is a result of below average rainfall which limited water availability and above average temperatures increasing actual evapotranspiration (see Climate overview). Soil moisture deficiencies in the region combined with above average evapotranspiration have contributed to below average streamflows in the rivers.
Streamflow
Figures W2 and W3 show streamflow pattern, volumes, and variation at two major rivers in the region:
- Colo River at Upper Colo in the Hawkesbury–Nepean catchment
- Shoalhaven River at Fossickers Flat in the Shoalhaven catchment.
The two river locations were selected for the following reasons:
- long-term flow data are available
- flows upstream of both river locations are unregulated and diversions are negligible
- both are major rivers in terms of flow volumes.
The Shoalhaven River experienced below average flows in the 2013–14 year except for July, September 2013 and April 2014 (Figure W2). Total annual flow for the Shoalhaven River for the 2013–14 year was 22% less than the long-term average for the period 1977–78 to 2013–14.
The Colo River experienced very much below average flows throughout the 2013–14 year except for April 2014 during which flow was a little less than average (Figure W3). Total annual flow for the Colo River for the 2013–14 year was 80% less than the long-term average for the period 1975–76 to 2013–14.
These below average to very much below average streamflows can be attributed to the rainfall and soil moisture conditions across the region during the 2013–14 year (see Climate overview and Soil moisture).
Figure W2 Graph of total monthly flow along the Shoalhaven River during the 2013–14 year compared with the long-term average and percentiles for the river
Figure W3 Graph of total monthly flow along the Colo River during the 2013–14 year compared with the long-term average and percentiles for the river
Major water initiatives
No major water initiatives were undertaken in the Sydney region during the 2013–14 year.