The main aim of this study was to develop an index to determine groundwater drought. Then, as a case study, for the sustainable use of groundwater, the optimum cropping pattern was determined in full compliance with the drought conditions in a plain. The newly presented index, known as the groundwater recharge drought index (GRDI), was determined based on the values of recharge in different zones in the plain. The GRDI for different zones within the region was calculated using the data covering 30 years (1980–2010). Based on this index, groundwater drought was found to occur frequently in these regions since 1981. According to the obtained results, the developed index, as compared with other indices, had several basic features including the ability to predict drought in groundwater, consideration of the possible effects of basin characteristics on groundwater drought, the capability of using different methods and models to calculate the GRDI, and separation of the human effects on the hydrological...

In this study, water flow over rectangular sharp-crested side weirs of various heights and widths was investigated. The distribution of the three-dimensional velocity over the crest and in the vicinity of the side weir was obtained using an acoustic Doppler velocity (ADV) meter. The structure of each component of velocity was examined separately. The velocity distributions showed that longitudinal velocity peaked near the beginning of the side weir, whereas velocity in the direction of spill flow was highest at the end of the weir. The observed values of vertical velocity showed that the direction of flow near the crest was upward, but at the highest depths, the flow direction was reversed and a downward flow was generated near the water surface. Analysis of the velocity profiles indicated that the local discharge increased along the crest of the weir; local discharge also increased as the relative width of the weir decreased. Since the angle of the spilling jet (φ) plays a large role in shaping t...

Circular-crested weirs are one of simplest types of hydraulic structures used for discharge measurement and regulation of open channel flow. In the present study, the flow over a circular-crested weir was simulated with an irrotational vortex to determine the weir discharge coefficient and velocity values over the crest. Two dimensionless parameters including circulation and curvature coefficient were defined and determined experimentally. The results show that these parameters could be presented by power equations. To develop and evaluate the proposed method, physical models of circular-crested weirs, containing various radii, heights and slopes, were investigated. It was found that this method produces the main features of weir flow reasonably well.