The last month's usage and inflow: Compare this to the same time last year. What about inflow versus outflow? A dam's level drops when more water is used (outflow) than flows in (inflow) obviously. This diagram shows cumulative outflow versus cumulative inflow for the entire system, using the SCA daily figures since November 2001. In other words we show for any moment how much water has been used (or entered the dams) since November 2001. Wince Nov 2001, the overall usage has been 4481.53 GL, whilst overall inflow has been 3784.03 GL (compare to the total capacity of Sydney's dams is just under 2400 GL). Note: when we discuss inflow, we refer to net inflow (i.e. after evaporation is taken into account). This is why the inflow figure can sometimes be below 0 (when evaporation is larger than actual inflows). Although inflow has not equaled outflow for the past few years, it is still very significant. This is one of the reasons why rainwater tanks in Sydney are still useful in drought conditions... it still does rain, just not so much. The inflow to the dams is inconsistent, however. The following graph displays daily usage and inflows since November 2001. The usage graph shows us that the Summers of 2001/2 and 2002/3 had higher usage, and otherwise there is a slight downward trend on water usage, water saving devices and general water consciousness on the part of consumers. Water restrictions up until level 3 have supposedly reduced water consumption by 12 percent. The large drop in usage in July 2005 corresponded to a fairly wet winter when the (relatively unpopular) desalination plant location was announced. It looks like people take shorter showers when an environmentally relatively unfriendly option is put forward. A more smoothed out version of this (a one-year rolling average) follows: Due to the smoothed nature of this graph, the trend is more clear. This is amplified when examined on a year-by-year basis: When inflow and usage are combined, a figure is arrived at which corresponds to the net gains (or losses) of the dams. This is represented int he following graph (showing Warragamba dam, and the other dams combined). A result greater than 0 represents an increase over a 365 day period for the dams. How low has Sydney's usage gone in the past few years? These tables show the record minimum usage for a single day and the record minimum average usage over an entire week. Date Day Usage ML 2002:01:01 2054 2003:01:01 1824 2004:01:01 1680 2005:01:01 1585 2006:01:01 1515 2007:01:01 1249 2008:01:01 1428 2009:01:01 1501 2002:01:02 2067 2003:01:02 1490 2004:01:02 1737 2005:01:02 1537 2006:01:02 1899 2007:01:02 1470 2008:01:02 1201 2009:01:02 1414 2002:01:03 2414 2003:01:03 1470 2004:01:03 1627 2005:01:03 1566 Date Week Usage ML/day 2002:11:05 2175 2002:11:06 2154 2002:11:07 2157 2002:11:08 2164 2002:11:09 2204 2002:11:10 2250 2002:11:11 2263 2002:11:12 2207 2002:11:13 2181 2002:11:14 2149 2002:11:15 2096 2002:11:16 2028 2002:11:17 1913 2002:11:18 1869 2002:11:19 1894 2002:11:20 1948 2002:11:21 1946 2002:11:22 1889 2002:11:23 1883 2002:11:24 1924 How is usage affected by rain and temperature in Sydney? We have already seen the effects of the 2001/2 and 2002/3 summers on water use, as well as the wet winter of 2005. The following graph compares water usage versus Sydney rainfall on the day before. In times of low rainfall, the usage is dependent on various factors, but when rainfall is high, the water use is quite consistently low. The wettest day (130+mm) of average usage was in 2002 just before a new level of water restrictions came into force. Temperature also has a large effect on water usage in Sydney. The following diagram shows that low temperatures equate to lower water usage. High temperatures can also match low water usage, however, as rain may occur to lower usage around such days. The effect of a change in our water usage on Sydney's dam levels? We have taken the data since November 2001 of Sydney's water usage and dam levels and calculated how full the dams would be under several alternative scenarios: 20% more usage of Sydney water 20% less usage of Sydney water 50% less usage of Sydney water If everyone had and used rainwater tanks for their irrigation and hand watering of their gardens whenever possible, usage would probably drop by around 20%. Hypothetical usage since 11.2001 Available water % full all dams 1 year change GL(%) 20% More 642.2 24.85 -103.22 (-3.99) As is 1538.5 59.53 -4.50 (-0.17) 20% Less 2434.8 94.22 94.22 (3.65) 50% Less 2583.6 99.97 78.77 (3.05) These calculations are of course just on figures since November 2001. When these figures are calculated back to 1998 when the dams were last full, a drop in usage would have produced more dramatic differences in dam levels now.

Sydney dam levels main page This month dam level statistics Rainfall this week Trends of Sydney dam levels Usage and Inflow trends Firefox Extension (SydDams) Interactive Catchment Map Dam levels for individual dams Sydney Desalination plant impact on dam levels Reduced Usage impact on dam levels How to save water in Sydney Rainwater tanks in Sydney Sydney's water restrictions General Information on Warragamba and Sydney's other Dams Home irrigation/watering systems in Sydney Old location of Sydney dam levels page Back to iliveinsydney.com Comments by visitors: Email webmaster@iliveinsydney.com if you need to contact the webmaster. I-live-in-sydney.com's subsite on Sydney's water is relevant to people interested in conserving water, rainwater tanks, irrigation, plumbing and plumbers. It can also be of interest to people examining water quality and filtering.