Cyprus-Forum.com

[repulsewarrior]

...thanks bill

[kurupetos]

Annanstasiades must be really excited with this...

[GreekIslandGirl]

Overall, the dams of the Republic are currently at 48.5% of capacity... same day last year the corresponding figure was 87.5% full.

The biggest, Kouris, is at 41.2 % capacity, Asprokremnos at 79.7%.

Looks like only Kalopanagiotis will overflow this year...

(Figs from CY Water Dev Dept)

They're not built so that they overflow to be useful. Overflowing is when their maximum volume capacity has been over-stretched. Half-full is probably the aim, to be safest.

[Paphitis]

Overall, the dams of the Republic are currently at 48.5% of capacity... same day last year the corresponding figure was 87.5% full.

The biggest, Kouris, is at 41.2 % capacity, Asprokremnos at 79.7%.

Looks like only Kalopanagiotis will overflow this year...

(Figs from CY Water Dev Dept)

They're not built so that they overflow to be useful. Overflowing is when their maximum volume capacity has been over-stretched. Half-full is probably the aim, to be safest.

Obviously it is a case if more is better! It would be better to be at 100% and have some overflow.

[bill cobbett]

Naturally, dams all over the world are designed to withstand being full, to be safe at 100% capacity.

Some of the dams of the Republic are connected so that an overflow from one high up feeds water to ones lower down.

... and it's also terribly important for dams to overflow so that rivers run, which in turn helps recharge the severely depleted aquifers.

(Dams in the Republic down to 48.1% capacity today)

[GreekIslandGirl]

It depends on the type of dam it happens to be, bill. The rivers shouldn't be affected as they are usually above the dam and overflow doesn't have far to go before it's lost to the sea anyway. Of course they are built to be safe with overflows; but overflowing is not using the dam to its maximum benefit (do we have any hydro-power?). As a general rule, they suffer huge evaporation problems the fuller they get. Certainly >90% full-to-capacity and overflowing leads to the greatest loss from evaporation for most types.

[After a quick search, I can't find any stats for the optimum capacity levels for the Cyprus dams.]

[supporttheunderdog]

Dams are normally built at the point where a long narrow valley begins to open out, and/or the land flattens. See picture.

image.jpg

Dams are basically intended to work at maximum capacity according to the available terrain and hopefully maintain the flow of water once full, so there is the most water available as well as to keep the river system reasonably full. However here Most of our rivers are seasonal and run dry in Summer, and the purpose of the dams is to store water from winter rains that would otherwise be lost to the sea.

We do not have Hydro as even a modest hydro requires a lot of water, and quite simply we do not have it. One needs to be in an area like Norway or Scotland with consistent precipitation to maintain dam levels to make it worthwhile. Here we do not have that luxury, well illustrated by the reduction in stored water compared to last year.

As for evaporation that is a function of surface area not percentage fill.

[GreekIslandGirl]

Of course evaporation is affected by surface area. Not as simple as that though. The higher the level of water (as capacity reaches max) the greater the surface area the water stretches over because most valleys tend to a V shape and certainly most dams fan out hence as the water level increases, so does the surface area and hence so does evaporation. As I said, each dam has it's optimum level and it is not engineered to require 100% fillage in order for this to be reached. It would be foolishly optimistic if that were the case.

(There are other factors at play too such as radiation from the sun increasing evaporation (reflectance? albedo?) and again the higher the dam is filled the greater this is - something to do with the height of water -> darker when high. There's another factor at play which is the temperature of the water and once a large volume warms up, it doesn't cool down as readily at night and hence the next day's losses are greater - a bit like how the sea stays warmer at night and evaporation increases - if the dam is 100% full then that body of water will stay warmer for longer. There's other factors too ...)