Thursday, March 18, 2010

Runoff and rainfall for the year thus far

The runoff from the March rains has ended. Thus, I think that this is a reasonable time to record how much runoff we have had for the year at this point.

The total runoff that I have tracked is: 16560.28 megalitres

However, this does not take into account runoff from rainfall in January and early February. ACTEW said that the runoff from that rainfall was 'effectively zero'. However, as I am not sure what they mean by that - they might simply mean 'it was very low - I am going to use the runoff per millimetre of rainfall rate to calculate the runoff.

This brings my total runoff for the year to: 19281.05045 megalitres.

This runoff is the result of 180 mm of rainfall.

It should be noted that we only got 43240 megalitres of rainfall last year, so we are doing much better by comparison.

Tuesday, March 9, 2010

March rainfall and runoff

There have now been two falls of rain in March. The first was 9.6 mm. This resulted in runoff of 457 megalitres, which was very low (half of the predicted runoff based on last year's runoff and rainfall figures.)

Then on 5,6,7 and 8 of March we had a combined rainfall of 38.2 (it was a fair bit more than that at our house, but I am going with the station that the BOM use.)

I am now tracking the runoff from this.

Currently, we have had 155.2 mm of rainfall since I started analysing this (way above average for the period) and less than 11,485 megalitres of runoff (way below average for that amount of rainfall, and below the megalitre per millimetre of runoff that we acheived last year, in what was a very low year.)

I expect that rainfall will be above average for the year, but runoff to be below average - well below average.