Niger, as part of its policy to preserve natural resources, passed laws in 1961 and 1962 establishing a northern limit to dry farming (the 16 in [400 mm] average annual rainfall isohyet
The southward movement of the isohyets
has also resulted in the southward migration of pastoralists into lands formerly occupied by sedentary farmers.
Traditionally, the dense isohyets
are depicted around the highest part of this upland (Galvonaitc et al.
A map of isohyets
(contours of equal rainfall) showing mean annual UAE rainfall for the 18-year period 1971/1972 through 1988/1989 indicates a figure for the western Ru'us al-Jibal in excess of 160 mm, but apparently not in excess of 180 mm (UAE University 1993, Plate 50).
The Gulf of Mexico can be divided into three broad geographic regions according to the weather patterns: eastern, southern and northwestern, because of the southwest-northeast trending isotherms and isohyets
that trend onshore in the northeast region (Douglas & Englehart 1981).
The Isohyetal method consists of recording the depths of rainfall at the locations of the various rain gauges and plotting isohyets
(lines of equal rainfall) by the same methods used for locating contour lines on topographic maps.
The GIS was used to generate mean annual temperature isotherms of 0.25 [degrees] C intervals and mean annual precipitation isohyets
of 1-cm intervals for the region.
Yet toward the south, in the region transitional to the Brazilian shield, the mean annual isohyets
are around 2,000mm (79in) (Sioli 1985).
Pulling out my old school Phillip's atlas (1969) showed that lines joining up places with equal rainfall ("isohyets
") join Liverpool up with Cheshire, the West Midlands and even parts of the South East all the way to the Kent coast!
The sandplain landscape of the northern wheatbelt of Western Australia lies between 28.3[degrees] and 30.7[degrees]S and 114.7[degrees] and 116.8[degrees]E, and between 300 and 400mm mean annual rainfall isohyets
. The area is characterised by deep, well-drained sands (Tenosols), yellow sandy loams and loamy sands (Kandosols), and clays (Vertosols and Dermosols) according to the WA Soil Group Classification (Schoknecht 2002) and Australian Soil Classification (Isbell 1996).