So, after they've taken the water, how much is left for residents?

Photo© C. Moneypenny

How much water does the DAMN company want to take out of the Petawawa?

Here is a very simple, non-scientific explanation using a generic river. It is not specific to the Petawawa other than the height (head) of 14 metres, as given by the DAMN company in late-April at a public meeting.

The energy available in flowing water depends on the volume of water flowing per second and the height (head) that the water falls. The conversion of this energy into electricity will depend upon the combined efficiency of the components; the efficiency of a small hydro scheme can be between 50-85%. I was generous and gave 70% efficiency.

The power contained by a body of water can be calculated by the following equation:

P = H x Q x g x e

Where:

P = power (kW)

H = head height (metres)

Q = flow rate (cubic metres per second or CMS)

g = gravitational constant (9.81 metres per second)

e = efficiency (0.5 ? 0.9, i.e. 50% - 85%)

So on the Petawawa... 14 (head height in metres) x 10 (cm/s) x 9.81 (gravity) x .7 (70% efficient)= 961.38 KW or roughly 1MW.

So that is approximately 10.5 CMS per MW.

The Dam company wanted a minimum 2 MW (21 CMS) to maximum of 10 MW (100 CMS).

Using 2007/08 as an typical example, and the newest available data from Environment Canada, the river flows vary from approx 15 CMS to just above 350 CMS, but were only over 100 CMS for April and May, only over 50 CMS in March, April, May and June, and below 20 CMS for Sept - February.

There are at least six months of the year minimum where it would be impossible to produce even 2 MW of power even if they were granted permission to remove every last drop of water from the river... unless they dam it and store it.

I realize that the proponent is non-commital about a "dam" versus a "diversion" until they finish their studies, but do the math yourself. I don't see how they hope to build this thing without a dam to store the water.

I checked against other years and all are similar to 2007. The flow rates of the Petawawa are taken from Environment Canada Water Survey of Canada date. The link is below.

References:

http://www.ecocentre.org.uk/hydro-power.html

http://www.oregon.gov/ENERGY/RENEW/Hydro/Hydro_index.shtml

http://www.wsc.ec.gc.ca/hydat/H2O/index_e.cfm?cname=graph.cfm
(Water Survey of Canada)