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Stream ordering is a useful property of every river network, having a wide range of applications. A method for determining stream orders that quickly and easily addresses various network topologies and magnitudes is therefore needed. This paper introduces a general recursive stream ordering framework for vector hydrography. It also presents a linear, O(n), stream ordering procedure for braided river networks, which is a major improvement to the existing quadratic, O(n 2 ), procedure. The discussion includes results and interpretations, and the appendices present procedure pseudocodes and thorough line by line explanations. (KEY TERMS: Strahler stream order; geographic information system; recursive algorithm; software; drainage; braided networks.) Gleyzer, Alexander, Michael Denisyuk, Alon Rimmer, and Yigal Salingar, 2004. A Fast Recursive GIS Algorithm for Computing Strahler Stream Order in Braided and Nonbraided Networks. Journal of the American Water Resources Association (JAWRA) 40(4):937-946.

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Causes of recent salinization of numerous plots in the Yizre'el Valley of Israel were examined through a detailed field study of two severely affected sites. In particular, the theory of artesian influence on salt build-up in the upper cultivated soil layer was investigated. Two piezometer nests and 12 wells were installed to study the subsurface hydraulic regime. Water samples and soil extracts were taken to characterize the chemical composition down to 10 m. No significant head differences were measured at the lower site, while at the upper site 96 per cent of the head that existed at the deep (7.5 m) artesian layer was dissipated within the overlying thick clay layer. Slight head differences were noted in the shallow layers. The deep-lying, coarse-textured aquifer differs markedly from the upper confining layers and constitutes an independent water body that has little relevance to surface processes. Chemical and hydrological analyses indicate that applied low-quality irrigation waters may be the primary cause of downward-moving salinity and alkalinity which, in turn, affect soil permeability and site productivity.