Multislit Weir Characteristics

The slit weir has been recently shown to be effective in measuring very small discharge rates. In this study, the slit weir concept is extended to permit one to measure both very low and very high discharge rates accurately. For this purpose, the hydrodynamic concept of images is adopted to form a bank of multislit weirs in which the individual slit weirs have nearly identical flow characteristics. The discharge coefficient of multislit weirs is determined experimentally using the measured discharges and the corresponding heads causing weir flow. The relationship between the discharge coefficient and the main dimensionless parameters is investigated. It is concluded that the discharge coefficient can be represented solely as a function of the Reynolds number.     

New Methodology to Evaluate Flow Rates in On-Demand Irrigation Networks

Although Clément methodology is the most commonly used model for obtaining the design flow rate in on-demand irrigation networks, studies have shown that the Clément methodology does not always fit properly. A new stochastic methodology is proposed in this paper [random daily demand curve (RDDC)], in order to achieve a more accurate design flow. Results from Clément and the proposed RDDC methodology are compared to measured flow data in an on-demand irrigation network located in Tarazona de La Mancha (Albacete, Spain). RDDC is shown to have a better fit with the measured data compared to the Clément methodology, which underestimated the design flow by 35%–40%. RDDC methodology avoids the problem of using average opening hydrant probability, resulting in a better estimation of the network behavior.     

Residential Irrigation Water Use in Central Florida

Automatic inground irrigation is a common option for residential homeowners desiring high-quality landscapes in Florida. However, rapid growth is straining water supplies in some areas of the state. The first objective of this study was to document residential irrigation water use in the Central Florida ridge region on typical residential landscapes (T1). The second objective was to determine if scheduling irrigation by setting controllers based on historical evapotranspiration (ET) (T2) and reducing the percentage of turf area combined with setting the controllers based on historical ET (T3) would lead to reductions in irrigation water use. The time frame of this study was 30?months beginning in January 2003. Irrigation accounted for 64% of the residential water use volume over all homes monitored during this project. The T1 homes had an average monthly water use of 149?mm/month. Compared to the T1 homes, T2 resulted in a 30% reduction (105?mm/month), and T3 had a 50% reduction (74?mm/month) in average monthly water use. Average monthly water use was significantly different (p<0.001) across the three irrigation treatments. Setting the irrigation controllers to apply water according to seasonal demand resulted in significantly less irrigation water applied. In addition, increasing the proportion of landscape area from 23% (T1 and T2) ornamental plants irrigated with sprinklers to 62% and irrigated with micro-irrigation (T3) resulted in the largest reduction in irrigation water applied. Compared to T2 where only the irrigation controllers were adjusted, this additional decrease in irrigation water applied was a result of low volume application on only a portion of the landscaped beds where irrigation is only applied to the root zone of plants.     

智能微喷喷灌设备的设计

针对现有微喷喷灌设备不能根据作物株高、种植行距、茎叶密集程度调整喷射幅宽和水量的问题,设计了智能微喷喷灌设备.介绍了设计方案,以及支撑机构、伸缩机构,分析了智能控制原理.所设计的智能微喷喷灌设备能够根据作物不同生长时期株高和茎叶密集程度的变化,调整喷灌范围.通过设置湿度传感器,可以实时采集作物所处环境的湿度情况,方便根...     

淠史杭灌区水量分配现状分析

文章分析了淠史杭灌区水量分配现状,对存在的问题提出了解决的对策.     

Evaluating the Potential of Quarry Lakes for Supplemental Irrigation

Population growth coupled with industrialization, increasing effects of climate change, and increasingly stringent water management regulations regarding the conservation of aquatic life are resulting in previously unknown agricultural water shortages in Padana Valley, Italy. To mitigate water shortage, it was recently proposed to use the water stored into numerous quarries of gravel material. Because quarry lakes are mostly located in the proximity of watercourses, aquifer drawdown induced by pumping can affect flow in nearby streams. The evaluation of the potential of quarry lakes for supplemental irrigation has to face stream depletion that is crucial from the perspective of the legal rights of the downstream users and ecosystem sustainability. The work presented in this paper investigates the potential of a quarry lake in Padana Valley to sustain irrigated crop water requirement during shortage periods. A simple and quite inexpensive technique for assessing streambed conductance based on streambed temperature measurements is presented. The results show that quarry lakes may be a promising alternative resource for supplemental irrigation during shortage periods, even when a watercourse is present in the surrounding area.     

Financial evaluation of renewable energy technologies for irrigation water pumping in India

An attempt to develop a simple framework for financial evaluation of renewable energy technologies (RETs) such as photovoltaic (PV) pump, windmill pump, biogas and producer gas-driven dual fuel engine pumps for irrigation water pumping has been made. The unit cost of water and unit cost of useful energy delivered by the RETs have been estimated. The monetary benefits that accrued to the end-user have been quantified in terms of the amount of diesel or electricity saved. Financial figures of merit for the investments made in the RETs have been estimated. The effect of fuel price escalation on these measures of financial performance has also been evaluated along with the estimation of the break-even prices of fuels likely to be substituted by RETs. Results of some exemplifying calculations are presented and briefly discussed.     

宝鸡峡渠首加坝加闸工程坝段岩基L_0缓倾角裂隙处理

宝鸡峡渠首加坝加闸工程 坝段基岩存在L0缓倾角裂隙,针对其特点,提出两种处理方法;根据工程进度计划、工程投资经济性、和工程质量的要求进行技术经济分析,采用大开挖的处理方法。     

A model for optimal sizing of photovoltaic irrigation water pumping systems

The previous methods for optimal sizing of photovoltaic (PV) irrigation water pumping systems separately considered the demand for hydraulic energy and possibilities of its production from available solar energy with the PV pumping system. Unlike such methods, this work approaches the subject problem systematically, meaning that all relevant system elements and their characteristics have been analyzed: PV water pumping system, local climate, boreholes, soil, crops and method of irrigation; therefore, the objective function has been defined in an entirely new manner. The result of such approach is the new mathematical hybrid simulation optimization model for optimal sizing of PV irrigation water pumping systems, that uses dynamic programming for optimizing, while the constraints were defined by the simulation model. The model was tested on two areas in Croatia, and it has been established that this model successfully takes into consideration all characteristic values and their relations in the integrated system. The optimal nominal electric power of PV generator, obtained in the manner presented, are relatively smaller than when the usual method of sizing is used. The presented method for solving the problem has paved the way towards the general model for optimal sizing of all stand-alone PV systems that have some type of energy storage, as well as optimal sizing of PV power plant that functions together with the storage hydroelectric power plant.     

Hazardous concentrations of selenium in soil and groundwater in North-West India

Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 μg L(-1)) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg(-1)) and Barwa (3.1 mg kg(-1)). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO(2) (40-62 wt.%), Al(2)O(3) (9-21 wt.%) and K(2)O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity.