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Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Subsurface pipe drainage has been the main engineering measure for saline-alkali land improvement, due to the easily mechanized operation, better control of saline-alkali soil without occupying cultivated lands. Two- or multi-stage pipe drainage system has been also widely used for easy maintenance and management in recent years. A photovoltaic power generation can serve as the power supply source of pipe drainage pump stations, particularly for simple and cost-saving. However, the solar photovoltaic water pump cannot operate smoothly, when the outlet of pipe drainage is submerged by a high water level at night. The capacity of the system can be greatly limited even to a complete loss. In this study, an improved capacity of drainage system was proposed for the solar photovoltaic subsurface pipe system in Liuzhong Town, Pingluo County, Yinbei irrigation area, in China. The feasibility of siphon auxiliary drainage was analyzed to determine the drainage capacity of the current system using the formula of siphon flow. Some parameters were then monitored to verify the improvement of drainage capacity, including the regional drainage discharge, the water level in the sump and drainage ditch, and groundwater level. The results show that there was a limited drainage capacity of the previous solar photovoltaic subsurface pipe system, where the drainage rate was less than or equal to 0.49 mm/d, far less than the drainage rate of 1.5 mm/d required by the standard control of salinization. Since the water level rose in the manhole at night, while the outlet of the subsurface pipe was submerged, the water level in the sump was restored to close to the groundwater level and higher than the water level of the adjacent drainage ditch. The positive difference in the water level between sump and ditch was more than 0.3 m. Alternatively, the siphon was selected for the auxiliary drainage at night, so that the drainage efficiency was greatly increased in the improved system. Since the diameter of the siphon was about 0.09 m, the drainage discharge at night was equivalent to that of the solar photovoltaic pump in the daytime. A vacuum pump and a few siphon pipes were added, indicating the low investment cost and being easy to implement. A horizontal connecting pipe between the sump and the adjacent drainage ditch was also added to realize the gravity drainage at night during construction. The findings can provide technical support for the application of solar photovoltaic subsurface pipe drainage systems. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Irrigation cutoff time is one of the important factors of irrigation management, and the determination of optimum cutoff time can effectively improve the irrigation performances. But for different irrigation conditions, the cutoff time of irrigation is very different, and it is difficult to directly determine the cutoff time of any given irrigation event. So, the cutoff control index of basin irrigation is used to study the cutoff control modes of basin irrigation. When the irrigation water is closed before the water advance to the end of basin, cutoff control index is equal to the ratio between the water advance distance when the irrigation water is closed and the basin length. On the contrary, R is equal to the ratio between the cutoff time and the time that water advance to the end. The optimization method of optimum cutoff time for basin irrigation was presented, and the minimum infiltration depth larger than zero and storage efficiency larger than 80% were set as the objective function to optimize cutoff time. One-dimensional hydrodynamic model of basin irrigation based on the hybrid numerical method was used to simulate the basin irrigation process. Combining the irrigation model with optimization method of cutoff time, the irrigation processes of 106176 irrigation events with different soil type, basin length, basin slope, land leveling precision and inflow rate were simulated, and for the same land leveling precision, the spatial variability of surface elevation was considered. For land leveling precision of 2, 3, 4, 5 and 6 cm, 4, 12, 15, 20 and 28 groups micro-topography data were respectively generated. The corresponding optimum cutoff time for each irrigation event was obtained, the influence of the irrigation factors on the optimum cutoff time was discussed, and the irrigation cutoff control modes were proposed. The irrigation data of typical fields were used to validate the rationality of the proposed cutoff control modes by comparing the irrigation performances under different cutoff time. Results showed that the optimum cutoff time of irrigation event was up to different irrigation factors. Cutoff control index changed with the basin length, basin slope, inflow rate and land leveling precision. Among these irrigation factors, the influence of slope and inflow rate on cutoff control index was the most obvious. Cutoff control index decreased with the increase of inflow rate. For the basins with the length of lower than 70 m, cutoff control index increased with the increase of slope, and for the basins with other lengths, cutoff control index conversely decreased with the increase of slope. Generally, cutoff control index decreased with the increase of basin length, but the influence of basin length on cutoff control index was obvious for the basins with >100 m length, when basin length was not more than 100 m, the influence weakened. The influence of land leveling precision was related with other irrigation factors, cutoff control index decreased with the increase of land leveling precision for <70 m basin, and increased with the increase of land leveling precision for other basins. By comparing the irrigation performances of typical basins under actual irrigation cutoff time and proposed cutoff control index, the rationality of proposed cutoff control index of basin irrigation was validated. For different basin length, slope, land leveling precision and inflow rate, the values of irrigation cutoff control index were presented. For the basins with the length of less than 70 m, the range of cutoff control index was 0.9-1.15. For most conditions cutoff control index should not be less than 1, but when basin slope was middle and leveling precision was not good, cutoff control index was about 0.9; and if slope was greater than 3‰ and land leveling precision was good, cutoff control index should not be less than 1.1. For the basins with the length of greater than 70 m and basin slope was less than 1‰, the range of cutoff control index was 0.8-1; but when basin slope was greater than 1‰, the range of cutoff control index was 0.75-0.95. The research results can supply reference for the cutoff control of basin irrigations, and the cutoff control index can be chosen according to the practical irrigation events. [ABSTRACT FROM AUTHOR]