Map courtesy of ARIC's Atmosphere, Climate & Environment Information Programme website.
Climatically this makes the western seaboard of the country very wet and conversely the eastern seaboard considerably dryer. As far as the Watershed is concerned rivers flowing westward tend to be smaller and shorter in length in comparison to those running eastwards, the massive River Severn being a notable exception. The map1 above, Fig 1., indicates areas of high and low precipitation but it could just as easily show high and low ground on a different scale.