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91.
The Shuttleworth and Wallace model (SW) was evaluated to estimate latent heat flux above a drip-irrigated Cabernet Sauvignon
vineyard, located in the Pencahue Valley, Region del Maule, Chile (35°22′ LS; 71°47′ LW; 150 m above sea level). The performance
of the WS model (LEws) was evaluated against the eddy-covariance method (LEed) on a 30 min time interval. Results indicate that the root mean square error (RMSE) and mean absolute error (MAE) were 29 W m−2 and 22 W m−2, respectively. For the vine evapotranspiration (ETv), RMSE was 0.42 mm day−1 and MAE was 0.36 mm day−1. The largest disagreements between LEed and LEws were observed under dry atmospheric conditions. Also, the sensitivity analysis indicates that predicted ETv by the SW model
was sensitive to errors of ±30% in leaf area index and mean stomatal resistance, but it was not affected by errors in the
estimation of aerodynamic resistances. 相似文献
92.
Performance of WATCOM (a numerical model) and CRPSM (a simple water balance model) were assessed in simulating root zone water
storage and water balance components under cowpea in Nigeria using a line source sprinkler system. Three sets of field data
were collected: the first was used for calibration and model parameters’ estimation and the other two for testing and comparisons.
The simulated soil water storage and crop evapotranspiration with WATCOM and CRPSM were in good agreement with field-measured
data though WATCOM performed significantly better (P < 0.05) under the stressed condition. The maximum average error between predicted and measured soil water storage was −0.95
and +1.47 mm for WATCOM and CRPSM, respectively, while that between measured and predicted actual crop evapotranspiration
was +2.7 and +11.38 mm, respectively, for the two models. WATCOM gave generally higher cumulative deep percolation and lower
evapotranspiration than that of CRPSM for all irrigation levels (P < 0.05), and values of deep percolation for WATCOM were in better agreement with field data than that of CRPSM. This suggests
that drainage below the field capacity needs to be included in CRPSM and that WATCOM will be a more useful management tool
when detailed soil parameter is required and under variable water regime. 相似文献
93.
Accounting for temporal inflow variation in the inverse solution for infiltration in surface irrigation 总被引:1,自引:0,他引:1
A simple modification of the volume balance equation of the IPARM model is presented to facilitate the use of variable inflow.
Traditional approaches for estimating infiltration from advance and/or runoff have merely considered the constant or step
inflow case. Whenever this assumption is violated, significant uncertainty is introduced into the estimated infiltration parameters.
Evaluation of the procedure with a number of data sets has demonstrated significant improvements in the estimates of infiltration
parameters. Furthermore, the technique has shown that a portion of the apparent variability in estimated soil intake rates
between furrows in the same field is a consequence of the constant inflow assumption. Accounting for the variable inflow to
estimate infiltration functions, both standardised the shape of the infiltration curve and reduced the magnitude of the variation
between curves. The proposed technique remains restricted by limitations similar to that of other volume balance models but
offers greater performance under typical inflow variations often experienced in practice. 相似文献
94.
A model for optimal operation of water supply/irrigation systems of various water quality sources, with treatment plants, multiple water quality conservative factors, and dilution junctions is presented. The objective function includes water cost at the sources, water conveyance costs which account for the hydraulics of the network indirectly, water treatment cost, and yield reduction costs of irrigated crops due to irrigation with poor quality water. The model can be used for systems with supply by canals as well as pipes, which serve both drinking water demands of urban/rural consumers and field irrigation requirements. The general nonlinear optimization problem has been simplified by decomposing it to a problem with linear constraints and nonlinear objective function. This problem is solved using the projected gradient method. The method is demonstrated for a regional water supply system in southern Israel that contains 39 pipes, 37 nodes, 11 sources, 10 agricultural consumers, and 4 domestic consumers. The optimal operation solution is described by discharge and salinity values for all pipes of the network. Sensitivity of the optimal solution to changes in the parameters is examined. The solution was found to be sensitive to the upper limit on drinking water quality, with total cost being reduced by 5% as the upper limit increases from 260 to 600 mg Cl l–1. The effect of income from unit crop yield is more pronounced. An increase of income by a factor of 20 results in an increase of the total cost by a factor of 3, thus encouraging more use of fresh water as long as the marginal cost of water supply is smaller than the marginal decrease in yield loss. The effect of conveyance cost becomes more pronounced as its cost increases. An increase by a factor of 100 results in an increase of the total cost by about 14%. The network studied has a long pipe that connects two distinct parts of the network and permits the supply of fresh water from one part to the other. Increasing the maximum permitted discharge in this pipe from 0 to 200 m3 h–1 reduces the total cost by 11%. Increasing the maximum discharge at one of the sources from 90 to 300 m3 h–1 reduces the total cost by about 8%. 相似文献
95.
A modern computer-based simulation tool (WaterMan) in the form of a game for on-farm water management was developed for application in training events for farmers, students, and irrigators. The WaterMan game utilizes an interactive framework, thereby allowing the user to develop scenarios and test alternatives in a convenient, risk-free environment. It includes a comprehensive soil water and salt balance calculation algorithm. It also employs heuristic capabilities for modeling all of the important aspects of on-farm water management, and to provide quantitative performance evaluations and practical water management advice to the trainees. Random events (both favorable and unfavorable) and different strategic decisions are included in the game for more realism and to provide an appropriate level of challenge according to player performance. Thus, the ability to anticipate the player skill level, and to reply with random events appropriate to the anticipated level, is provided by the heuristic capabilities used in the software. These heuristic features were developed based on a combination of two artificial intelligence approaches: (1) a pattern recognition approach and (2) reinforcement learning based on a Markov decision processes approach, specifically the Q-learning method. These two approaches were combined in a new way to account for the difference in the effect of actions taken by the player and action taken by the system in the game world. The reward function for the Q-learning method was modified to reflect the suggested classification of the WaterMan game as what is referred to as a partially competitive and partially cooperative game. 相似文献
96.
97.
Reducing overall water diversions for agriculture, while maintaining or increasing production to keep up with increasing world
population, has been and will continue to be a challenge. Yet there is not good agreement regarding the programs needed to
improve the productivity of agricultural water use, nor what increases are feasible. It is recognized that field irrigation
is inherently nonuniform. So also is the distribution of water to users and water delivery service nonuniform. Here, we suggest
that crop-scale irrigation uniformity can be examined at a project scale by understanding how field, farm and project irrigation
systems contribute to nonuniformity. We also discuss the interrelation between project scale uniformity and the relative irrigation
water supply, and their combined impact on project productivity. We provide an example which relates internal measures of
project performance (e.g., water distribution operations) and external measures of project performance (e.g., project-wise
water productivity). 相似文献
98.
PCB removal,soil enzyme activities,and microbial community structures during the phytoremediation by alfalfa in field soils 总被引:1,自引:1,他引:1
Chen Tu Ying Teng Yongming Luo Xianghui Sun Shaopo Deng Zhengao Li Wuxing Liu Zhihong Xu 《Journal of Soils and Sediments》2011,11(4):649-656
Purpose
An in situ phytoremediation trial was developed in order to investigate the function of alfalfa during a 2-year bioremediation of an agricultural soil contaminated with polychlorinated biphenyls (PCBs). The study was conducted with the aim to better understand the application potential of PCB phytoremediation at field scale. 相似文献99.
Contaminant transport to groundwater systems through the unsaturated zone follows, in most cases, preferential pathways. The
understanding and assessment of this preferential flow mechanism is important to the prevention and solution of resulting
problems. A column study was carried out where a NaCl-tracer solution (33 to 37 mmohs/cm of conductivity) was passed through
an intact soil core under saturated conditions and three different ponding heights ranging from 5 to 30 mm. Outflow rates
varied from 13 to 103 ml/min during the three tests performed. A subsequent dye tracing and slicing of the soil column was
performed. Electrical conductivity measurements assessed indirectly the chloride content of the water outflow. Breakthrough
curves (BTCs) showed short threshold times (less than 20% pore volume time) and asymmetry with respect to the point defined
by C/Co = 0.5 and pore volume time. The BTCs successfully represent the flow measurements through the soil column, this fact
is supported by the subsequent horizontal slicing (5 cm thick) of the intact core. 相似文献
100.
Three soil classification systems—the World Reference Base for Soil Resources (WRB), Soil Taxonomy, and the recent Russian system—were used for the identification of 17 soil profiles in southwestern Poland; all the systems put emphasis on the soil properties as diagnostic criteria. Different soils developed on glaciofluvial plains, loessic uplands, and in the Sudetes Mountains were classified. The best correlation between the classification decisions in the different systems was obtained for the most widespread soils owing to the similarity of the diagnostic criteria, which were essentially close although not coinciding. The most prominent divergence between the systems in both the names and the taxonomic categories of the soils was found for the polygenetic soils and for the soils developing from the lithologically discontinuous parent materials. It was also found that the diagnostic elements differ in terms of their taxonomic importance among the classification systems. 相似文献