The flow of water in the Lower Ebro is controlled by adjusting the gates on the dam further upriver at Flix. The normal flow is around 420 cubic metres per second. On Monday this rose dramatically to 1,450 m³/s! The nearest Gauging Station a couple of miles upriver recorded a rise of over 4 meters in the water level. It’s an awesome sight to see the volume of water increase by this amount in only a couple of hours. As it rises and covers the riverbanks it flushes out all sorts of debris and we see huge rafts of twigs, dead vegetation and other matter – even entire dead trees – go sweeping past. In fact, the reason for the flood is to clear the river of the invasive algae that tend to proliferate in stretches of slack water.
As far as wildlife is concerned there are winners and losers and it was interesting to observe the goings on. As the river rose and submerged the vegetation the House Martins, Swifts and Swallows had a feast as all kinds of insects and flies took to the air to escape the rising water. A pair of Black Kites circled the slowly diminishing river island for over an hour. Twice I saw one of them snatch something from the surface of the water – perhaps a vole or mouse. Later, when I was walking our dogs a couple of displaced snakes were swimming around near the edge of the water. Directly in front of our house there is a wall above the river bank. We had noticed previously that a female mallard was nesting in a hole near the base of the wall. It was difficult to tell from peering over the wall whether the water level had reached the hole but we feared for the ducklings when late afternoon we saw her out on the surface of the water staying close to the area where the nest was.
The flushing of the river was scheduled to last until 23.00hrs. Sure enough when we rose on Tuesday morning the river was at its normal level.
Today I’ve noticed a female mallard hanging around with 3 males. All the courtship behaviour stopped weeks ago so I’m guessing that this is our “wall duck” and that she lost her brood yesterday. Meanwhile House Martins have re-commenced work on a 3rd nest on our house. It was started about 10 days ago and then came to a halt. Today they are busy building away – perhaps all the fresh mud on the bank has renewed their enthusiasm!
Floods of course are a normal part of river life. Before the dams were built the river would flood naturally in Spring as the rivers filled with Spring rains and snowmelt. In those days, not only wildlife but people too were at the mercy of the whims of the river. If ever you visit here you will notice several plaques attached to buildings both on this street and on the street behind showing where the river rose to in certain years. Indeed, in our garage, at a height of about 10 feet there is a mark scratched into the wall indicating the water level in 1907. I would imagine that surpassed being awesome and was pretty damn scary!
Here are some pics for comparison of this weeks flood: