Reinstated a small pond on the allotment. Apparently the original pond was scrapped by the previous tenant when he stepped in it! So having cleared the debris and excavated the hole a bit I put a new liner down and part filled it with water from a nearby trough, the rain can do the rest.
  I particularly want to encourage frogs to spawn. Frogs don't eat fruit and veg but they are partial to slugs and snails.