In K19 the River Witham should not be confused with the North Hykeham Pump Drain which whilst being also filled with water is not the same. The Witham is of course a natural feature of the landscape whilst the drain is not.
The Witham will quite probably contain fish though not to my knowledge, salmon. The drain may also contain fish but it is less likely to do so than the river. In any event you should take care when out walking with small children that the youngsters keep well away from the edge of the water. It can be very dangerous especially after a period of heavy rainfall. The banks can get slippery.
I mentioned salmon because I quite like salmon sandwiches. Either smoked or poached with a bit of cuke and mayonnaise. Brown bread not white and butter not margarine. You should eat a variety of sandwich fillings in order to provide a varied diet. Just salmon every day would get a bit boring and you might find yourself short of a specific vitamin. This is guesswork.
I am somewhat digressing here. Artistic license. I did look online to see what information I could find about the drain. I was hoping to find the date where it was cut/invented (delete as appropriate). I couldn’t. At least on the first two pages of Google and I wasn’t desperate enough for the information to look any further.
So that’s it. Not a particularly enlightening article but it’s all you’re getting. Ciao.