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1.
This study was conducted on an irrigated area of southern Italy to analyze the current operation of a large-scale irrigation delivery system and the effects of the operation procedures on crop irrigation management and aquifer salinity increase. The area is characterized by relatively high levels of groundwater salinity in the summer that are probably due to intensive groundwater pumping by farmers during periods of peak irrigation demand, with the resulting seawater intrusion. Two alternative delivery schedules, namely the rotation delivery schedule and the flexible delivery schedule, referred to as RDS and FDS, respectively, were simulated using a soil-water balance model under different combinations of crop, soil and climatic conditions. The first set of simulations concerned the farm irrigation management constrained by the rotational delivery used by the local water management organization. The second scenario simulated the farm irrigation schedule most commonly used by growers in the area for maximizing crop yields. Based on crop irrigation management under RDS and FDS, two alternative operational scenarios were also developed at the scheme level and then compared for evaluation. Winter and summer salinity maps of the aquifer were developed by interpolating salinity measurements of the groundwater samples collected during the 2006 irrigation season. From these maps, a close relationship can be inferred among delivery schedule, aquifer exploitation and salinity increase, which justifies the need for implementing FDS that might reduce the groundwater demand for irrigation.  相似文献   

2.
Changes in the hydrologic balance in many irrigation areas, including those in the Murray Basin, Australia, have resulted in high watertables and salinity problems. However, where suitable aquifers exist, groundwater pumping and subsequent irrigation application after mixing with surface waters (referred to as conjunctive water use) can control salinity and watertable depth and improve productivity of degraded land. In order to assess where conjunctive water use will successfully control salinity, it is necessary to estimate the effects of pumped groundwater salinity on rootzone salinity. A simple steady rate model is derived for this purpose from mass conservation of salt and water. The model enables an estimate to be made of rootzone salinity for any particular salinity level of the groundwater being used in conjunction with surface water; this enables calculation of the required crop salt tolerance to prevent yield reductions. The most important input parameters for the model are groundwater salinity, the annual depth of class A pan evaporation, the annual depth of rainfall, the salinity of irrigation water, and a leaching parameter. For model parameters nominated in this paper, where groundwater salinity reaches 5 dS/m a crop threshold salt tolerance greater than 1.6 dS/m is required to avoid yield reductions. Where groundwater salinity approaches 10 dS/m, a crop threshold tolerance of 3 dS/m is required. Whilst the model derived indicates that rootzone salinity is sensitive to groundwater salinity, rootzone salinity is insensitive to leaching for leaching fractions commonly encountered (0.1 to 0.4). The insensitivity to leaching means that it could be expected that similar yields could be attained on heavy or light textured soils. This insensitivity also implies that there is no yield penalty from increasing the mass of pumped salt by pumping to achieve maximum watertable control in addition to leaching. The model developed is also used to estimate yield reductions expected under conjunctive use, for any particular levels of groundwater salinity and crop salt tolerance.  相似文献   

3.
该文在研究作物耐盐性的基础上,提出咸淡水联合运用的策略——实行咸淡水轮灌与混灌,可以减缓盐分对作物的危害,改善土壤环境,增辟灌溉水源,扩大灌溉面积,夺取农业丰收。  相似文献   

4.
华北平原纯井灌区水资源严重不足。限水灌溉是保持地下水平衡、农业可持续发展的必要条件,通过对作物耗水规律及地下水动态规律的分析,在保持地下水多年平衡的前提下,不追求个别年份高产,以多年粮食总产量最高为目标,提出了地下水均衡开采的调节配水模型,并采用非线性规划理论对该模型进行了论证。应用该模型可计算出不同水文年地下水开采量及各作物灌溉定额,进而计算灌溉制度,可广泛应用于纯井灌区的井灌工程的规划设计。  相似文献   

5.
A weekly irrigation planning LP model is formulated for determining the optimal cropping pattern and reservoir water allocation for an existing storage based irrigation system in India. Objective of the model is maximization of net annual benefit from the project. In an irrigation planning of a storage based irrigation system, initial storage of the reservoir at the beginning of the reservoir operation, expected inflows into the reservoir during each intraseasonal period, capacity of channels, crop calendar and yield response to water deficit in each growth stage of crop play a vital role in deciding acreage and water allocation to each crop. The planning model takes into account yield response to water deficit in each intraseasonal period of the crop, expected weekly inflows entering into the reservoir, storage continuity of reservoir, land and water availability, equity of water allocation among sub areas and proportionate downstream river release. One year comprising of 52 weeks is considered as planning horizon. To account for uncertainty in water resources availability, the model is solved for four levels of reliability of weekly inflows entering into the reservoir (90%, 85%, 80% and 75%). Alternative optimal cropping patterns and weekly releases to crops grown in each sub area under each main canal are obtained for various states of initial storage at the beginning of reservoir operation and for various levels of weekly inflows into the reservoir. Results reveal the importance of initial state of reservoir storage for feasible solution and shows the impact on cropping pattern with the change in initial storage of reservoir for different levels of reliability of weekly inflows.  相似文献   

6.
The long term sustainability of conjunctive water use for controlling irrigation salinity is affected by increase in groundwater salinity over time. This paper uses mass conservation of salt and water to assess groundwater degradation over long time scales. Management options which affect this rate of degradation are also examined. The groundwater model developed is illustrated using data from the Shepparton Irrigation Region in the Murray Basin, Australia. The model predicts rapid groundwater deterioration when conjunctive use is conducted over only a fraction of the area of influence of a groundwater pump. Where the pumped aquifer is underlain by deeper groundwaters, the rate of groundwater degradation is also affected by leakage into or out of the conjunctive use system. Surface redistribution of groundwater from pumps installed in zones of regional groundwater discharge to areas recharging the regional groundwaters, reduces excessive degradation in the zones of discharge. With optimal surface distribution of groundwater, the rate of degradation is low. The rate of groundwater degradation also depends on salt inputs from irrigation water and rainfall, and the average depth from the soil surface to the base of the aquifer. The rate of degradation resulting from applied salts in surface water and rainfall is typically about 0.01 dSm-1 per year for shallow aquifers in the Shepparton region, but the rate is lower where deeper aquifers are pumped. Partial irrigation also reduces the rate of degradation because of the reduced rate of salt inputs. Where poorer quality groundwater lies within the area of influence of the groundwater pump, a greater rate of deterioration in the quality of pumped groundwater can be expected from groundwater mixing. In some irrigation regions limited export of groundwater through surface water conveyance structures to a river is possible, so that a regional surface salt balance could be maintained. However, salt exports made equal to the rate of surface imports into the irrigated area will only significantly impact groundwater salinity in the very long term, or where only shallow aquifers can be pumped. In addition, this export can be costly for downstream water users, or if construction of additional conveyance infrastructure is extensive; export can have a detrimental impact on riverine ecosystems. Other management options such as the depth of pump installation and the spatial distribution of irrigation water and pumped groundwater, which affect the redistribution of salts within the groundwater system, have the potential to have a much greater impact on local groundwater salinity.  相似文献   

7.
Waters of poor quality are often used to irrigate crops in arid and semiarid regions, including the Fars Province of southwest Iran. The UNSATCHEM model was first calibrated and validated using field data that were collected to evaluate the use of saline water for the wheat crop. The calibrated and validated model was then employed to study different aspects of the salinization process and the impact of rainfall. The effects of irrigation water quality on the salinization process were evaluated using model simulations, in which irrigation waters of different salinity were used. The salinization process under different practices of conjunctive water use was also studied using simulations. Different practices were evaluated and ranked on the basis of temporal changes in root-zone salinity, which were compared with respect to the sensitivity of wheat to salinity. This ranking was then verified using published field studies evaluating wheat yield data for different practices of conjunctive water use. Next, the effects of the water application rate on the soil salt balance were studied using the UNSATCHEM simulations. The salt balance was affected by the quantity of applied irrigation water and precipitation/dissolution reactions. The results suggested that the less irrigation water is used, the more salts (calcite and gypsum) precipitate from the soil solution. Finally, the model was used to evaluate how the electrical conductivity of irrigation water affects the wheat production while taking into account annual rainfall and its distribution throughout the year. The maximum salinity of the irrigation water supply, which can be safely used in the long term (33 years) without impairing the wheat production, was determined to be 6 dS m?1. Rainfall distribution also plays a major role in determining seasonal soil salinity of the root zone. Winter-concentrated rainfall is more effective in reducing salinity than a similar amount of rainfall distributed throughout autumn, winter, and spring seasons.  相似文献   

8.
Using AquaCrop to derive deficit irrigation schedules   总被引：2，自引：0，他引：2  
Straightforward guidelines for deficit irrigation (DI) can help in increasing crop water productivity in agriculture. To elaborate such guidelines, crop models assist in assessing the conjunctive effect of different environmental stresses on crop yield. We use the AquaCrop model to simulate crop development for long series of historical climate data. Subsequently we carry out a frequency analysis on the simulated intermediate biomass levels at the start of the critical growth stage, during which irrigation will be applied. From the start of the critical growth stage onwards, we simulate dry weather conditions and derive optimal frequencies (time interval of a fixed net application depth) of irrigation to avoid drought stress during the sensitive growth stages and to guarantee maximum water productivity. By summarizing these results in easy readable charts, they become appropriate for policy, extension and farmer level use. We illustrate the procedure to derive DI schedules with an example of quinoa in Bolivia. If applied to other crops and regions, the presented methodology can be an illustrative decision support tool for sustainable agriculture based on DI.  相似文献   

9.
Measuring groundwater extractions is central to adequate groundwater management in agricultural basins. Groundwater pumping records are often subject to considerable uncertainties, particularly in the case of arid and semiarid settings where irrigation is the most important water use. In most cases this is due to the difficulties involved in locating and monitoring all wells. We describe the estimation of groundwater pumping by coupling the water table fluctuation method with the groundwater balance equation. This is demonstrated through its application to the Mancha Occidental aquifer, Spain, an area subject to intensive pumping for irrigation since the early 1970s. A sensitivity analysis is conducted to evaluate the effect of relevant hydrogeological parameters, namely specific yield, as well as the most appropriate theoretical semivariogram, to calculate yearly storage variations within the system. Results are validated in the light of official pumping estimates.  相似文献   

10.
The objective of the Spanish government-funded GESMO project is to research on new water policy evaluation and monitoring tools, applied to aquifer 8/23 in the Eastern Mancha, which covers one of the most important areas under the charge of the Júcar Catchment Confederation. The project is to output two types of end products: Decision Support Systems for defining water use policies, including economic impact and environmental simulators within a single multi-criteria decision-making environment and Measure Monitoring and Control Systems employing tele-detection and simulation of crop water needs. The Decision Support Systems will include three, highly complex, theoretical models in a single information technology product: a three-dimensional aquifer 8/23 behavior simulation model, an econometric model to predict crop allocation depending on the economic environment, water availabilities, etc., and an automatic alternative generation and evaluation system based on a multi-criteria methodology. The objective of the system is to advise on possible water policies and how they would materialize into spatially and temporally distributed water quotas (m3/ha) with the objective of both safeguarding the aquifer in the medium and long term and increasing the economic profitability of regional agriculture. In this paper, a regional econometric model is presented for studying the impact of water use quotas on the main irrigated crops allocation in the region.  相似文献   

11.
In the assessment of plant response to the climate changes, the effects of CO2 increase in the atmosphere and the subsequent rise of temperatures must be taken into account for their effects on crop physiology. In Mediterranean areas, a decrease of water availability and a more frequent occurrence of drought periods are expected. The objective of this study was to assess the impact of elevated CO2 concentration and high temperature on reference evapotranspiration (ETo) and crop evapotranspiration (ETc) in the Mediterranean areas. The Penman-Monteith equation was used to simulate the future changes of reference evapotranspiration (ETo) by the recalibration of the canopy resistance parameter. Besides, crop coefficients (Kc) were adjusted according to the future climate trend. Then the modified empirical model (ETc = ETo × Kc) was applied providing an effective quantification of the climate change impact on water use of irrigated crops grown in Mediterranean areas. In the studied area, water use assessment was carried out for the period from 1961 to 2006 (measured data) and for a period from 2071 until 2100 (simulated data), showing a future climatic scenario. Water and irrigation use of crops will change as a function of climate changes, thermal needs of single crops and time of the year when they grow. Climate simulation model foresees the tendency for a significant increase of temperatures and a decrease of total year rainfall with a change of their distribution. The temperature increase and the concomitant expected rainfall decrease lead to a rise of year potential water deficit. About the autumn-spring crops, as wheat, a further increase of water deficit, is not expected. On the contrary, for spring-summer crops as tomato, a significant increase of water deficit and thus of irrigation need, is foreseen. Actually, for crops growing in that period of the year, the substantial rise of evapotranspiration demand cannot be compensated by crop cycle reduction and partial stomatal closure.  相似文献   

12.
Water transfers within mixed crops systems are complicated to understand due to the large number of complex interactions between the various components. Standard techniques fail to provide the proper assessment of the components of the water balance. Experiments and modeling developments are used to understand the dynamics of water transfers within the association of olive trees with annual crops under irrigation in Central Tunisia. The whole system is represented by a unit area made up of three components: a plot with the annual crop, a plot with the olive tree and a plot of bare soil. The modeling approach is based on the concept of reservoir. The model works on a daily time step and accounts for the lateral transfers of water occurring between the components of the system: (i) the water uptake by the roots of olive trees; (ii) the physical flow of water between the irrigated plot and the non-irrigated ones. A field experiment was carried out during 2 years (2002, 2003) and three crop cycles (spring potato, spring pea and autumn potato) in order to calibrate the model and test its validity. Olive tree transpiration was estimated from sap flow measurements and soil moisture in the different compartments was measured by neutron probe technique. The experimental data compare fairly well with the model outputs. The first purpose of the model is to understand the functioning of the olive tree–annual crop association from a water standpoint, but it can be easily extended to other intercropping systems mixing perennial vegetation with annual crops or used as a management tool. The estimates of the water extracted by the olive trees in each reservoir appear to be much more significant than those of the water physically transferred between reservoirs.  相似文献   

13.
Due to urban growth, some agricultural lands have been replaced by residential, municipal, and industrial areas. In some cases the remaining agricultural land will not have enough water because of transfers from agriculture to M&I (municipal and industrial) users. Therefore, in many places, especially in arid and semi-arid regions, the use of treated wastewater as a reliable source of irrigation water has already been, or will be, considered in the future. Due to its unique characteristics, this new resource has many challenges that cannot be ignored, such as health issues, water quality, and long- and short-term effects on soils and crops. The study described herein considered the development of a new GIS-based model for planning and managing the reuse of treated wastewater for the irrigation of agricultural and green lands, considering various factors such as population and urban growth. The model is composed of several different modules, including an urban growth model. These modules are designed to help in the decision-making process for allocations of water resources to agricultural areas, considering factors such as crop types, crop pattern, water salinity, soil characteristics, pumping and conveyance costs, and also by comparing different management scenarios. Appropriate crops that can be grown with a specific water salinity and soil characteristics, proper water resources for each farm (according to pumping and conveyance costs, and analysis of water demand, and water supply) can be determined through the application of this model. The model can also rank agricultural areas and open spaces in and near an urban area according to their suitability for irrigated agriculture.  相似文献   

14.
This paper develops a non-linear programming optimization model with an integrated soil water balance, to determine the optimal reservoir release policies, the irrigation allocation to multiple crops and the optimal cropping pattern in irrigated agriculture. Decision variables are the cultivated area and the water allocated to each crop. The objective function of the model maximizes the total farm income, which is based on crop–water production functions, production cost and crop prices. The proposed model is solved using the simulated annealing (SA) global optimization stochastic search algorithm in combination with the stochastic gradient descent algorithm. The rainfall, evapotranspiration and inflow are considered to be stochastic and the model is run for expected values of the above parameters corresponding to different probability of exceedence. By combining various probability levels of rainfall, evapotranspiration and inflow, four weather conditions are distinguished. The model takes into account an irrigation time interval in each growth stage and gives the optimal distribution of area, the water to each crop and the total farm income. The outputs of this model were compared with the results obtained from the model in which the only decision variables are cultivated areas. The model was applied on data from a planned reservoir on the Havrias River in Northern Greece, is sufficiently general and has great potential to be applicable as a decision support tool for cropping patterns of an irrigated area and irrigation scheduling.  相似文献   

15.
Artificial subsurface drainage is not an option for addressing the saline, shallow ground water conditions along the west side of the San Joaquin Valley because of the lack of drainage water disposal facilities. Thus, the salinity/drainage problem of the valley must be addressed through improved irrigation practices. One option is to use drip irrigation in the salt affected soil.A study evaluated the response of processing tomato and cotton to drip irrigation under shallow, saline ground water at depths less than 1 m. A randomized block experiment with four irrigation treatments of different water applications was used for both crops. Measurements included crop yield and quality, soil salinity, soil water content, soil water potential, and canopy coverage. Results showed drip irrigation of processing tomato to be highly profitable under these conditions due to the yield obtained for the highest water application. Water applications for drip-irrigated tomato should be about equal to seasonal crop evapotranspiration because yield decreased as applied water decreased. No yield response of cotton to applied water occurred indicating that as applied water decreased, cotton uptake of the shallow ground water increased. While a water balance showed no field-wide leaching, salinity data clearly showed salt leaching around the drip lines.  相似文献   

16.
This paper analyzes the effect of water supply uncertainty on farmers’ choice of crop portfolio. The paper presents an innovative model to estimate the value of uncertainty of water supply, and then tests the model using data from Israel. The modeling results provide support to the hypothesis that uncertainty induces farmers to prefer crops whose growth requires less agricultural capital accumulation, despite their lower profitability (agricultural capital referring to trees and other plants which take a significant period of time to mature). This is due to the risk that in a given year water supply will fall below a certain minimal level, thereby causing loss of all accumulated capital. The paper also examines a government intervention policy for mitigating uncertainty: use of reclaimed wastewater in crop irrigation as a supplement for freshwater supply. The costs associated with constructing the required wastewater reclamation and supply facilities are compared to the benefits of additional farm income earned through a more certain on-farm water supply. It is shown that under certain conditions implementation of this policy is indeed economically worthwhile.  相似文献   

17.
黄水河流域地表水地下水联合调度模型探讨   总被引：1，自引：0，他引：1  
结合黄水河流域实际情况探讨并建立基于供水量准则的黄水河流域地表水地下水联合调度模型,并以1997年数据调算地表水地下水联合调度模型,从调算结果表明在黄水河流域进行地表水地下水联合调度充分利用了水资源并且可以防止地下水超采。  相似文献   

18.
A model for optimal allocation of water from a single-purpose reservoir to an irrigation project with pre-determined multiple cropping patterns was developed. The model consisted of two modules: (I) the intra-seasonal allocation model (non-linear programming) which is used for allocation of water among different crops for a definite combination of state variables (inflow class, rainfall class, reservoir storage classes at the beginning and at the end of the season) for the non-dormant season to maximize total farm income; and (II) the seasonal allocation model (stochastic-dynamic programming) which is used for the convergent operating policy over seasons for optimal expected farm income over a year. The model was applied to Ardak reservoir dam (I.R. Iran) in an arid region. Low river inflow in the dormant season at the study area could not admit the reservoir class changes for specific combinations of state variables, and therefore resulted in a non-usable result. Imposing a fictitious positive relative net benefit for all possible combinations of reservoir class changes eliminated this problem. It was also shown that rainfall did not play a marked role in the study area, which is an arid region, and its stochastic nature can be removed from the model.  相似文献   

19.
A tool named DOPIR (Dimensioning Of Pressurized IRrigation) was developed to optimize the process of water abstraction from an aquifer for pressurized irrigation systems. This tool integrates the main factors throughout the irrigation process, from the water source to the emitter. The objective is to minimize the total cost of water abstraction and application (C T) (investment (C a) + operation (C op) per unit of irrigated area according to the type of aquifer, crop water requirement and electricity rate periods. To highlight the usefulness of this tool, DOPIR has been applied to a corn crop in Spain with a permanent sprinkler irrigation system, considering two types of aquifer: confined and unconfined. The effects of parameters such as the static water table in the aquifer (SWT), irrigated area (S), number of subunits in the plot (NS), sprinkler and lateral pipe spacing, and average application rate (ARa) on C T have been analyzed. Results show that energy cost (C e) is the most important component of C T (50–72 % in the case studies). Thus, it is very important to adapt the design and management of the irrigation and pumping system throughout the irrigation season to the energy rate periods.  相似文献   

20.
依据水量平衡原理,在阿勒泰地区通过大田小区试验与理论分析对打瓜耗水规律进行了研究。用以探究北疆地区打瓜开花坐果期和果实膨大前中期耗水规律,旨在为打瓜的灌溉制度提供理论指导。研究结果表明:耗水量与产量显著相关,且打瓜开花坐果前期耗水量中期后期果实膨大中期前期。但在土地贫瘠的情况下,作物耗水规律有可能出现"休养"情况。因此应在开花坐果期和果实膨大前中期在这两个时期应注意对作物进行水分与养分的补给,以增加作物产量,提高产品品质等。对于作物灌水需求程度,主要由该时期作物对水分敏感程度所决定。但各时期对水分敏感程度显著不同,因此需要对各生育期进行定量分析,以探究各生育期单独的最佳灌水定额。  相似文献   

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