According to remaining records it was Lord Molyneux who struck first. Knowing he was in a powerful position ( with marriage links to powerful Lords and a voice at court), Molyneux claimed the entire great common, including the Moss Lake, as his, and claimed that he could do what he liked with it. As it turned out, he interpreted this 'right' as being able to send some of his peasant workers to build dams under cover of dark to change the flow of water into and out of Mosslake fields. The immediate impact was twofold.
First, the fields previously providing peat for his rival Sir Edward Moore flooded, meaning turf couldn’t be cut, and Molyneux thus gained a temporary monopoly on the peat business, driving prices up.
Second, by damming up the northernmost stream which Moore used, he ensured that the water, following the laws of gravity and of Lord Molyneux ( though mainly the former) now flowed copiously down the southern stream, powering mills in Toxteth Park and hitting the business of the water-powered mills in the other direction.
It’s also worth noting that in 1635, Lord Molyneux had taken control of the wind and horse-powered Townsend and Eastham mills at the North end of the Town. Blocking up the flow to the remaining water mill at Eastham Dale ( modern day Byrom Street) meant that Moore's business received a double hit. His Eastham Dale mill lost out to none water-reliant competitors, and at the same time the Toxteth Park water mills of Molyneux thrived.
As Moore plaintively complained ( rather petulantly given that his motives were exactly the same), 'this was against the natural order'. Moore's own fields were lower down the slopes, he argued, so were the natural route and flow of the water downhill, and his competitor was breaking not just the laws of the land, but those of nature itself. So... to restore the ‘natural order’ he naturally built his own dam and dug a ditch to further guide the stream where he needed it to go again. This was done quite carefully and gradually, as Molyneux had more influence should the matter ever reach the law courts ( this at a time when who you knew was openly more important than justice).
The turf war resulted in a fantastically useful diatribe for historians from the pen of Sir Edward, explaining just how important the draining stream from MossLake fields was. While I doubt it was his prime motive, in retrospect it helps show how Liverpool was able to expand and begin its path to maritime domination.
Besides there are two great reasons wherefore the town ought to keep that water-course the right and usual course, which, if otherwise, it may prejudice the town very much: the first is, there is no water-course convenient or about the town for skinners, dyers, or other such trades, as this is which makes the continual water stream which runs down the Goyt to the Pool bridge, so that if this stream should be turned, such tradesmen will have no encouragement; the second reason is, if ever the Pool be cut navigable, of necessity all such cuts wherein ships are to ride, must either have a considerable fresh stream to run continually through it or it will quickly wrick up, or else there must be convenient places for raising great dams of water to let out with floodgates when necessity requires for cleansing of the channel ; and truly God and nature hath made all the places between the Pool and the stone plate so convenient for raising excessive great dams, and that so convenient out of the way, to the prejudice of none, and then to supply these dams, so great a fresh from off the moss lake, that though my eyes may never see it, yet I am confident that God Almighty, which makes nothing in vain, hath ordained this to be the greatest good for this town. Therefore I hope the town will never lose the advantage of the water coming that way; for if they do, all they are worth cannot procure a stream to cleanse the pool, as above said. If once you are of the council, your oath obliges you to care for the good of the town ; and if you be not, your interest is so involved with theirs, that take this for a warning from me, that if they prosper you must thrive, and if the town sink you must drown : so as where a finger be cut off, the whole body feels it; so you, in your interest, being a member of that body, it can receive not the least scar either in loss or repute,
From The Moore Rental
While not entirely philanthropic in his thinking, Sir Edward was no fool. The expanding industry of the town needed a fresh water stream for all the ancillary industries connected with maritime trade. Without this running through the business areas of the town, the skinners, dyers and tanners who provided export and trade goods, and supported the sailing industry, would have no reason to set up shop there.