Broads Surface Water Changes

[Timbo]

I thought Vaughan and a few others might find this interesting. A map of the northern Broads showing the increase and decrease in surface water levels comparing measurements taken between 1984-1999 and 200-2015.

Green is an increase in level and red is a decrease in level. Filby Broad seems to be drying up!

There are a whole range of maps like this available at Earth Time. Interesting stuff!

[dnks34]

Drying up or silting up!!

[Guest]

I wonder whether there's any correlation between the areas which are drier and the amount of agricultural and drinking water abstraction. I think Great Yarmouth takes a lot of it's drinking water from the 'Trinity Broads' and it's a fair bet that we use a lot more of it now. There was also a problem between a 'landowner' and farmers in the Barton Broad area, when it was found that Sutton Fen was drying out and excessive agricultural water abstraction was thought to have been the reason.

[Vaughan]

Hmm. . . . 

I have been gazing at this for 10 minutes but I am afraid it doesn't "shout" a lot at me.

Kingfisher is quite right that the Trinity Broads would show a lower level as they are used for abstraction of water for Yarmouth. But aren't they still connected to the river system via the old Fleet Dyke?

We don't know what the actual range of rise and fall is. It must be a very small amount, otherwise why are some parts of the coastline green and others are red? It's the same North Sea, isn't it?

The Hickling area shows green - no surprise there - and yet the Thurne itself shows no change. Strange, since we all know you can't get under Potter bridge any more!

I would like to see further south, from Acle across the Halvergate marshes and on across the Waveney Valley to Beccles. I would also like to see the survey start from 1964 and not 1984. Reason for this is that in 1984, the programme of deep-dyke drainage with protective flood banks, to convert marshland into arable farms, had been almost completed. So if you started the survey in 1964 you should see higher levels in the rivers but much lower levels in the land around, nowadays, compared to earlier.

 

[Guest]

I was just looking at that map again and the only 'pattern' I can see is,  the green areas (ie: water increase) appear to be those directly joined to the river system. Which would suggest that river levels have risen. Those not directly joined to the river system, appear to be the mostly red areas (ie: water decrease). Although the 'Trinity Broads' are joined to the River Bure, via 'Muck Fleet' it appears there is a sluice (or similar) at the confluence. I would imagine the sluice would only be opened to release water from the 'Muck Fleet' and it's adjoining drainage dykes, into the Bure, when levels were too high. Due to the salinity of the water in the lower River Bure, the sluice would probably be kept closed at high river/tide levels, to prevent saline incursion into 'Muck Fleet' and upwards to the 'Trinity Broads' which is a drinking water abstraction point. The fact that most of the red areas are 'land locked' would lead to the assumption that the water table is probably lower now, perhaps due to increased water abstraction, lower rainfall, more effective land drainage, possibly a combination of all three.