Evaluation of the Stability and Suitable Scale of an Oasis Irrigation District in Northwest China

Oases support human activities in arid and semiarid regions, and their stability is important for regional sustainable development and water resource management. Water consumption is the major factor affecting the stability of oases. On the basis of remote sensing images, evaporation and socioeconomic data, this study first evaluates the stability of the Dunhuang Oasis against the expansion of an oasis irrigation district and planting structure changes from 1987 to 2015. Next, it calculates a suitable area of the oasis irrigation district using water–energy balance theory. The results are as follows: (1) During the 1987–2015 period, with the expansion in the oasis irrigation area, the planting structure underwent a marked transformation from food crops to cash crops to orchards. Water consumption pattern likewise changed considerably. (2) The stability of the Dunhuang Oasis continued to weaken from 0.54 in 1987 until it reached a dangerously unstable level of 0.17 in 2010. With the implementation of water-saving measures and a water-transfer project, the stability of the Dunhuang Oasis irrigation district increased to a metastable level of 0.22 in 2015. (3) Setting the stability are 0.5 of a stable level and 0.75 of an extremely stable level, and the oasis irrigation district should be impractical and reduced by 168 and 241 km2 to attain a suitable oasis ecosystem scale. Hence, at present, the water-transfer project is the most practical way to increase allocated water resource to the oasis irrigation district for improving its stability.

Metastable level properties of the excited configuration 4p64d84f

Metastable levels in rhodium-like ions with the ground configuration 4p64d9 and the excited configurations 4p64d84f and 4p54d10 are investigated. The ab initio calculations of the level energies, radiative multipole transition probabilities are performed in a quasirelativistic Hartree–Fock approximation employing an extensive configuration interaction based on quasirelativistic transformed radial orbitals. Systematic trends in the behavior of calculated radiative lifetimes of the metastable levels are studied for the ions from Z = 60 to Z = 92. The significance of the radiative transitions of higher multipole order (M2 and E3) for the calculated radiative lifetimes is demonstrated and discussed.