To pond or not to pond

I have a pond in one of my paddocks. It's come about because about a metre & a half down, there's pipe that goes nowhere (except to a metre & a half underground in the middle of the paddock). Until quite recently it was underneath a big concrete pad - I reckon it might have been there, uncapped, pumping out water unnoticed for the last few decades.

So I dug a big hole & found the pipe, then I got a plumber in & set him loose. He braised a cap on the end of the pipe & all was well. For a month or so. And then a new pond formed a couple of metres in from the cap. Clearly the pipe is old & munted.

So I have a choice now... I can get the plumber back in & try & figure out where this old pipe is coming from (probably 100 mtres or so back underneath the gate or thereabouts) & disconnect it from the mains, or whatever the plumbing terms are.

Or I could dig a nice big hole over the pipe, line it with weedmatting & river stones & tell everybody we have a spring.

I bought the weedmatting already.

Point to note, our part of the coast has no water restrictions ever, and so far, no water metering. And one day in the future we will be digging trenches & stuff & laying new water pipes, so I daresay we'll find where it joins one day.

So whaddya all think. Would this work anyway? And should I do it?