攀西地区农业开发条件、潜力与对策

攀西地区位于四川省的西南部,包括攀枝花市和凉山州的全部。幅员面积6.75万km~2,1988年末人口为437.3万人。攀西不仅矿产、水能资源举世瞩目,而且光热资源丰富,宜农荒地资源多,农业开发条件好、潜力大,是国家原材料、能源和农业开发的重点地区。本文拟就种植业为重点,对攀西农业开发条件、潜力和对策进行分析论证,以引起社会重视,使之尽快列为全国农业开发的重点区,进行先期开发。     

POLICY IMPACTS ON AGRICULTURAL IRRIGATION ELECTRICITY DEMAND IN THE COLUMBIA BASIN1

ABSTRACT: Accurately estimating the price elasticity of demand for irrigation electricity is important to major electricity suppliers such as the Bonneville Power Administration (BPA) of the Pacific Northwest. The BPA has a revenue maximization objective, and the elasticity of demand is central to its rate setting process. Several studies have attempted to estimate demand for irrigation electricity, but none has explicitly included federal agricultural policy and program variables. Tins paper discusses how agricultural programs may influence farmers irrigation decisions and thus their demand for irrigation electricity. It suggests that existing programs serve to make farmers more responsive to electricity rate increases than would otherwise be the case. Thus, studies that fail to include them may underestimate the responsiveness of farmers to electricity rate increases.     

IMPACTS OF AGRICULTURAL DRAINAGE WELL CLOSURE ON CROP PRODUCTION: A WATERSHED CASE STUDY1

ABSTRACT: Much of north-central Iowa is characterized by flat topography, shallow depressions, and poor natural surface drainage. Land drainage systems comprising of tile drains and agricultural drainage wells (ADWs) are used as outlets for subsurface drainage of cropland under corn and soybean production. Studies have shown that these drainage systems, mainly the ADWs, are potential routes for agricultural chemicals to underground aquifers. To protect the region's vital groundwater resource, researchers are evaluating alternative outlets ranging from complete closure of existing ADWs (and creation of wetlands) to continued use of ADWs and chemical management in a comprehensive policy framework. This paper presents the results of a study designed to provide government jurisdictions, farmers, and land managers information for assessing the impact of closing ADWs on crop production. The study couples a geographic information systems database for a 471-hectare watershed in Humboldt County, Iowa, with a groundwater flow model (MODFLOW) and an empirical crop yield loss model to predict long-term effects of complete closure of ADWs on crop production. The cropland areas inundated and the relative crop yield loss due to ADW closure are determined as a function of long-term climatic data. The results indicate that elimination of drainage outlets in the watershed could result in ponding of low-lying areas and poorly drained soils, making them unsuitable for crop production. Such wetness also decreases the efficiency of production in the no-ponding areas by isolating fields, and the crop yield loss can be reduced by an annual average of about 18 percent.     

土地利用变化对农业自然灾害灾情的影响机理(一)──基于实地调查与统计资料的分析

上地利用变化不仅影响区域灾情的结构与类型,还深刻影响其灾情程度．本文以处在北方农牧交错带中段、深受旱灾影响的内蒙古乌兰察布盟为案例,基于统计资料及野外调查,剖析了在气候干旱化程度加剧、农作物成灾面积在波动中增大的趋势下,粮食产量在波动中增长的机理．结果表明,在上地利用中,粮食作物种植结构及其面积比例的调整,增强了粮食生产系统抵御农业自然灾害的能力。因此,调整上地利用结构是一种有效的减灾措施．     

DEVELOPMENT AND EVALUATION OF A DIMENSIONLESS UNIT HYDROGRAPH1

ABSTRACT: A generalized unit hydrograph method is developed and evaluated for ungaged watersheds. A key component in this method is the value of a dimensionless storage coefficient. Procedures to estimate this coefficient are given using calibrated values from 142 rainfall-runoff events gaged in watershed located mainly in the Eastern US. Only limited success was obtained in predicting this storage coefficient. Thirty-seven, independent rainfall-runoff events were used to test the proposed technique. The generalized unit hydrograph predicted the observed runoff hydrographs fairly well with considerable improvement in accuracy over the SCS dimensionless unit hydrograph. Approximately one-half of test storms had percent errors in predicted peak flow rates that were less than 34 percent compared to percent error of 88 percent with the SCS method.     

AN ARCHETYPAL LINEAR PROGRAMMING MODEL FOR OPTIMAL INTERTEMPORAL ALLOCATION OF GROUNDWATR TO AGRICULTURAL ACTIVITIES1

ABSTRACT: In the past, researchers have applied a variety of analytical techniques for maximizing the present value of a stock resource - simulation, calculus of variations, stochastic dynamic programming, and optimal control theory. This paper presents a more operational approach - linear programming. A simplified, broadly drawn example from Southwest agriculture is used for demonstrating the model's structure and output. The method is based on a set of state transformation operations that prevent the additivity assumption of linear programming from being violated.     

A CONCEPTUAL FRAMEWORK FOR EVALUATING AGRICULTURAL WATER CONSERVATION POTENTIALS1

ABSTRACT: This paper defines types of water losses in irrigated agriculture and outlines potentials for water conservation. Recoverable water “losses” (seepage, leakage, and spillage during storage and conveyance, and surface runoff and deep percolation during irrigation) and irrecoverable losses (evaporation from water and soil surfaces and transpiration from plants) are described and illustrated. Some conservation terms are defined, particularly the distinction between on-farm irrigation efficiency and areawide efficiency. Briefly reviewed are agricultural water conservation technologies and their applicability. The biggest untapped potential for water conservation may be a reduction in irrecoverable losses, especially evapotranspiration. The advantages and disadvantages of reducing recoverable and irrecoverable water losses are described, including possible effects on ground water, energy, salinity, crops, wildlife, and in-stream uses. Such information may be useful in several policy and management issues, e.g., ground water overdraft and possible constraints on crops and sites to be irrigated.     

OPTIMIZING NONPOINT SOURCE CONTROLS IN WATER QUALITY REGULATION1

ABSTRACT: A stochastic programming framework is developed to evaluate the economic implications of reliability criteria and multiple effluent controls on nonpoint source pollution. An integrated watershed simulation model is used to generate probability distributions for agricultural effluents in surface and ground water resulting from agricultural practices. Results from the planning model indicate that reliability and multiple effluent constraints significantly increase the cost of nonpoint controls but the effects vary by control alternative. The analysis indicates that an evaluation of multiple water quality objectives can be an important planning tool for designing nonpoint source controls for innovative programs to promote cost-effective water quality regulation.     

EVALUATION OF MANAGEMENT PRACTICES TO CONTROL AGRICULTURAL POLLUTANTS1

ABSTRACT: The objective of this study was to evaluate the effectiveness of various land-use practices upon the production of nonpoint source pollutants from small agricultural watersheds in Northern Virginia. Pollutant production at each watershed was determined by individual monitoring stations. Data analysis consisted of a determination of the site specific pollutant yield for similar watersheds subjected to differing crop management approaches. These collected data were then compared to those generated by a parametric, event model developed for this investigation. This synthetic data base was used to eliminate or reduce errors resulting from monitoring site differences and to extend the collected data for additional comparisons.     

PREDICTING IMPACTS FROM WATER CONSERVATION AND ENERGY DEVELOPMENT ON THE SALTON SEA,CALIFORNIA1

ABSTRACT: An input-output model was developed to predict changes in Salton Sea salinity and water level until the year 2000 due to proposed water conservation efforts and geothermal and solar pond energy developments. The model SALINP provided good agreement with the observed salinities for 1960–80. While SALINP was not overly sensitive to one-year changes in any of the major inputs, a change in the historical means of the Imperial Valley runoff and evaporative loss inputs produced a significant effect on future predictions. The proposed water conservation measures caused the predicted Salton Sea salinity for 2000 to greatly exceed 40,000 ppm, the level at which adverse effects to wildlife are believed to occur. The possible geothermal development also produced predicted salinities considerably above 40,000 ppm. The salinity predictions for solar ponds by themselves and in conjunction with geothermal development were below 45,000 ppm for 2000. The solar pond and geothermal combination also resulted in a predicted lowering of the “natural” water level by 5 to 7 feet by 2000.