Looks very similar to the installation on the Billing in Rawdon. In this case one has a stone built pump house alongside a similar earthed over structure. The semi buried structure is a large concrete water tank/cistern used to boost the pressure in the 1920's water system to Rawdon and Yeadon. The doored vestibules contain/contained valves that regulated the in and outflows. On the Rawdon installation there are a number of 'swan neck' air vents in the roof of the cistern.
Just to explain, it's most likely a pumping station for an aquifer. The brick building would have housed generators and pumps which have now been replaced by more modern pumping sets which will be contained in the green plastic enclosure (mostly obscured by lens flare in the pic).
At a guess the modern pumps probably negate the need for the reservoir, so it's probably disused now.
On many of the inter war years larger scale OS maps these installations are marked with the name or the initials of the private water company that owner the installation, after Nationalisation just technical terms are used.