1. College of Water Resources and Architectural Engineering Northwest A&F Univ. Yangling Shaanxi Province 712100 PR China
2. Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education Northwest A&F Univ. Yangling Shaanxi Province 712100 PR China
3. Dep. of Civil Engineering Faculty of Engineering Univ. of Peradeniya Peradeniya 20400 Sri Lanka
4. College of Natural Resources and Environment Northwest A&F Univ. Yangling Shaanxi Province 712100 PR China