Daily dam levels - weekly changes and trend for the last month. Stats updated each week. 2012-04-26 Overall Available GL(%) 2500.5 (96.85%) Weekly change GL(%) -13.00 (-0.50%) Monthly change GL(%) 36.50 (1.41%) Yearly change GL(%) 583.00 (22.58%) Overall dam levels and usage for the last month. In the month up to 2012-04-26 the dam levels have gone from 2462.5 GL (Gigalitres) to 2500.5 GL. Usage and inflow for the last month: You can compare this situation to what it was like a year ago. Current Trends At the overall rate of water loss in the past week in the dams, our supply will last 1346 days, less than 4 years and run out on 2016-1-2 . At the overall rate of water gain in the past month in the dams, they will fill in 62 days, less than 1 years and will overflow on 2012-6-27 . At the overall rate of water gain in the past year in the dams, they will fill in 813 days, less than 3 years and will overflow on 2014-7-18 . To fill the dams we would need about 35 mm of rain over a fortnight.

Overall dam levels since November 2001 This figure shows the data since November 2001 for overall dam levels. CSV of raw data format is: year, month, day, dayofyear, Bulk water supply (usage), Available storage,temperature,rainfall. From SCA website. You can see this in more detail in the year-by-year figure below. This figure shows the overall dam levels for the last few years. Each line represents how full the dams are for that year. What about inflow versus outflow? The reason a dam's level drops is that more water is used (outflow) than flows in (inflow). The following figure shows cumulative outflow versus cumulative inflow for the entire system, measured daily since November 2001. In that time the overall usage is 5349.39 GL, whilst the cumulative inflow is 5613.89 GL (note that the overall capacity of the system is a little under 2400 GL). Note that when measuring inflow, this is net inflow (after evaporation is taken into account). This is why net natural inflow can sometimes be negative. You can see that although inflow has not equaled outflow, it is still significant. This is why rainwater tanks in Sydney are still valuable in drought conditions. Day by day, however, the inflow to the dams is not very consistent. The following figure shows the daily usage and daily inflow since November 2001. From the usage we can see that the summers of 2001/2 and 2002/3 had high usage, and otherwise there is a slight downward trend on water usage, presumably due to water restrictions, water saving devices and general water consciousness on the part of consumers. A version of this figure with a one-year rolling average is presented here. Once again these aspects are shown more clearly when we look at the data year by year. The general trend of each year to consume less water than the previous year is quite obvious. How do rain and temperature affect water usage? We have already seen the effects of the 2001/2 and 2002/3 summers on water use. What about the effects of rain and temperature on daily consumption? The following graphical representation shows water usage versus Sydney rainfall on the previous day. On low rainfall times the usage is dependent on various factors, but when rainfall is high, the water use is quite consistently low. The really wet day (130+mm) that was of average usage was in 2002 just prior when strict water restrictions came into operation. Temperature also has an effect on water usage. This graphical representation shows that low temperatures mean low water usage. High temperatures do not guarantee high water usage, as rain can also occur as a thunderstorm on the afternoon of a hot day. What effect would a change in our water usage have on dam levels? The following table and graph examine what the current dam levels would be under various alternative water use scenarios. For example what would have happened if we had been using more water since November 2001, for example with no water restrictions or a higher population? Or what would have happened if we had been using less water in that time? For example, if everyone had rainwater tanks for their irrigation and hand watering of their gardens, usage would probably drop around 20%. Hypothetical usage since 11.2001 Available water % full all dams 1 year change GL(%) 20% More 1430.6 55.41 501.24 (19.41) As is 2500.5 96.85 583.00 (22.58) 20% Less 2551.8 98.84 -20.38 (-0.79) 50% Less 2553.2 98.89 -28.03 (-1.09) These calculations are just on figures since November 2001. If we had been using less water since the dams were last full in 1998 then dam levels would be even higher! What effect would a desalination plant have on our dam levels? The government has built a desalination plant. If an additional 500ML desalination plant had been in place and operating since November 2001, a significant difference in our dam levels would be noticeable, as the following data indicate. Desalination plants do use a lot of electricity. One way to reduce the electricity load is to only turn on the desalination plant whenever the water level drops below 50%. We have also included this possibility in our figures and table below. Hypothetical since 11.2001 Available water (GL) % full all dams 1year change GL(%) As is 2500.5 96.85 583.00 (22.58) 100 ML/day 2551.25 98.81 289.65 (11.22) 500 ML/day 2552.85 98.88 -28.00 (-1.08) 500 ML/day when levels < 50% 2826 109.46 583.00 (22.58) The 500ML/day option appears to be able to hold the dam levels close to steady under drought conditions, hence may only need to be operated when dam levels are low. A 100ML/day plant would need to operate continuously to have much effect. Hence, should rainfall conditions return to the 1960-2000 average and usage not increase much, the 500 ML/day plant may use significantly less electricity overall as it could be turned off most of the time! In other words, as the dams (historically) often vary between 80% and 100% full, a 100ML/day plant may waste energy delivering water when the dams may soon fill, while not providing sufficient water should the dams fall below 50%. Of course, if the recent extended dry spell is more permanent, then the 500ML/day plant would be required (given current usage) to maintain Sydney's water supply. What effect would the Shoalhaven Transfer scheme have on our dam levels? A scheme has been announced in which flows from the Shoalhaven Scheme to Sydney would be increased. The basic idea is that the Shoalhaven catchment is rather large and close to the coast (hence inflows are large) and Tallowa Dam often overflows, even under drought conditions (link provides graphs and stats on Tallowa Dam). If this had been in place and operating since November 2001, a significant difference in our dam levels would be noticeable, as the following data indicate. We also examine the combination of such a scheme and a 500ML/day desalination plant. Note that we have estimated the effect of the stage 1 and 2 Shoalhaven scheme by 80,110 GL/year respectively. The actual net gain of water in Sydney's dams is much harder to calculate as it concerns the amount of water which currently overflows from Tallowa that would otherwise have been captured. As noted above, in the past few years of drought conditions, Tallowa has still often overflowed and hence this scheme would have helped in this drought. Hypothetical since 11.2001 Available water (GL) % full all dams 1year change GL(%) As is 2500.5 96.85 583.00 (22.58) Stage 1 3333.8 129.12 662.72 (25.67) Stage 2 3645.8 141.21 692.56 (26.82) Stage 2 + desal 2554.05 98.92 -27.80 (-1.08) If Stage 2 of the Shoalhaven transfer scheme were in place in late 2001, as well as a 500 ML/day desalination plant (both in full use) then the dams would be sufficiently full that there would be not even a thought of a dam level problem. Even without a desalination plant, this proposed scheme would have had a big impact on our dam levels. 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 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 Relevant External links: Warwick Hughes page on Sydney rainfall trends 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.