Extreme rainfall and drinking water quality: a regional perspective

Abstract

Record high, extreme rainfall intensities were observed in South East Queensland, Australia in January 2011, resulting in drinking water storages above capacity and subsequent floods. This paper focuses on changes, and subsequent recovery, in water quality due to sediment and nutrient loading associated with these high inflows across the region's water supplies. In total, 8 systems were routinely monitored and results indicate that storages with larger and more degraded catchment areas experienced greater declines in water quality relative to storages with smaller, less disturbed catchments. A case study focussing on Wivenhoe Dam, the primary water supply for the region, revealed large scale sediment inputs to the system, estimated to between 1.5 and 20 million tonnes. These were accompanied by high nutrient and metal loads, and water column turbidity above water quality guidelines persisted for a period of at least 6 months after inflows. Given the increased likelihood of such intense inflow events in the future, sound catchment management appears imperative to reduce negative impacts on storage water quality.

Tracking Inflows in Lake Wivenhoe during a Major Flood Using Optical Spectroscopy

“…The resultant runoff rapidly filled Lake Wivenhoe to 190% of its designed storage capacity. The surrounding catchment is heavily modified with only 40% remnant vegetation, and this, combined with the record inflows, resulted in a significant pollutant loading, including sediment, dissolved organic matter and nutrients, over a very short period of time [1].…”

Near-Bed Monitoring of Suspended Sediment during a Major Flood Event Highlights Deficiencies in Existing Event-Loading Estimates

“…Laidley Creek is located in South East Queensland, Australia (Figure 2A), a sub-tropical region prone to large, irregular rainfall events [8]. The creek has a catchment surface area of 462 km 2 and runs for approximately 60 km, with much of the course through highly erodible alluvium plains.…”

Reducing the turbidity of the Brisbane River Estuary, Australia

“…For context, estimates of the sediment trapped by Wivenhoe dam are included and discussed. Estimates for the total load of sediment captured by Wivenhoe dam during the 2011 floods range between 1.5 and 21 million tonnes (Grinham et al, 2012). Unfortunately the SSC measurements for Gregor's Creek, the most significant tributary into Wivenhoe dam, was incomplete with measurements only collected whilst inflows were 8 times smaller than at the peak.…”