The rapid growth of the industrial cities of Leeds and Bradford during the 18th and 19th centuries necessitated the establishment of a plentiful and reliable source of water for the future.  To cater for this growing demand, many reservoir sites were developed across the eastern and western the Pennines.  In the AONB, 11 reservoirs were constructed between 1875 and 1966 reflecting its gritstone topography coupled with high rainfall, rapid run-off and an impervious geology.

Scar House and Angram reservoirs at the head of Nidderdale supply drinking water directly to Bradford via a strikingly engineered system of underground stone-lined tunnels and above-ground aqueducts. Work on the lower Scar House dam was completed in 1932; the remains of the village built to house construction workers are still visible as is their legacy of the  massive dam wall, spillways, pumping houses and other structures.  

The then Leeds Corporation acquired the majority of the Washburn Valley in the southern half of the AONB to develop four reservoirs:  Lindley Wood in 1875, Swinsty in 1876, Fewston in 1879 and Thruscross which opened in 1966. Together with Gouthwaite reservoir in Nidderdale, water from Lindley Wood is used to compensate for drinking water abstraction from the river Wharfe.

Further north in Colsterdale, Harrogate Corporation completed work on Leighton and Roundhill Reservoirs in the early part of the 20th Century. Water from Roundhill is fed into Yorkshire Water's grid whilst Leighton is used to compensate for abstraction from the river Ure near Masham.

In their development, many valley bottom settlements, textile mills, watercourses, communities, pasture and arable land were lost and the valley landscapes significantly altered as a result.  On several occasions during periods of drought in the last 15 years, when reservoir levels have sharply declined, the framework of the flooded landscapes (including the remains of West End village at Thruscross) have become visible again.

However, the reservoirs are an integral element of the AONB's landscape, providing new habitats for flora and fauna, contributing to the historic environment and creating extensive recreational opportunities such as fishing and walking.