This large body of water near Billericay has some nice woodland walking trails at its southern end. There's a good size parking area at the end of Giffords Lane, off South Hanningfield Road. From here you can pick up the walking trails, heading west through Well Wood and Hawk's Wood. There's nice views over the water, pretty grazing meadows and a waterside cafe near the car park. Look out for lots of bluebells in the spring months.
The area is also a significant nature reserve with lots of wildfowl to look for on the reservoir. From the bird hides you can see coot, gadwall, tufted duck, pochard, shoveler, shelduck and great crested grebe. There's also a good visitor centre with information, refreshments, toys, books, birdfeeders and feed.
The St Peters Way long distance trail runs past the northern side of the water. It will take you through the countryside from West Hanningfield to East Hanningfield.
Just a couple of miles south west of the reservoir you will find Norsey Woods. The 165 acre site includes waymarked woodland trails with lots of wildlife to look out for around the ponds and streams.
The site is also located close to Danbury Common and Danbury Country Park where there are more good walking trails.
Just to the east is the lovely Marsh Farm Country Park in South Woodham Ferrers.