playas are low-lands which is considered to be the locations of accumulation of superficial and ground waters fromhigher elevations and these waters have different types of salts and various salinity level. therefore, because of lack ofrainfall and fresh-water both for human and animal useage or even for plants, it is needed to apply proper methods toharvest fresh water from these saline-waters...

Planar locally finite graphs which are almost vertex transitive are discussed. If the graph is 3-connected and has at most one end then the group of automorphisms is a planar discontinuous group and its structure is wellknown. A general result is obtained for such graphs where no restriction is put on the number of ends. It is shown that such a graph can be built up from one-ended or finite pla...