WATER YIELD IMPROVEMENT BY VEGETATION MANAGEMENT1

ABSTRACT: Vegetation management aimed at increasing the amount of usable water yield from precipitation falling on upstream watersheds may be one alternative for supplementing water supplies. Indications are that water yields can be increased within a multiple-use framework, which can benefit or at least be compatible with other natural resource objectives. Through changes in vegetation on a watershed, it is possible to reduce evaporation losses only slightly but significantly increase streamflow runoff. In an assessment of potentials for water yield improvement in Arizona, experimental studies on various vegetation zones are reviewed. Because of either limited acreage or limited rainfall, the alpine, grassland, aspen, and desert shrub vegetation zones are not realistic management areas for Arizona. Furthermore, manipulation of pinyon-juniper woodlands does not appear promising at this time. Conversion of chaparral to grasses and forbs does appear to be a possible treatment for water yield improvement, as well as various silvicultural treatments of mixed conifer and ponderosa pine forests. Streamflow increases are given for experiments in chaparral, mixed conifer, and ponderosa pine vegetation zones. However, complete information on possible constraints for these zones is not currently available. Specific assessment of water yield management options for riparian vegetation is difficult to make, due to incomplete knowledge of water yield changes and other constraints for this vegetation zone. Prior to the final adoption of management practices, results of experimental work must be coupled with economic and social considerations.     

A review of sediment predictive techniques as viewed from the perspective of nonpoint pollution management

User-oriented criteria for the evaluation of physically based management models are presented. These criteria emphasize the utility rather than the elegance of the model. The standards are then applied to efforts at predicting non-point pollutant loadings. In particular a critical review of sediment pollution is used as the basis for the evaluation of sediment yield models as management tools. A wide range of sediment yield models are rated and recommendations for their use are made.     

PREDICTING BASE FLOW USING HYDROGEOLOGIC PARAMETERS1

ABSTRACT: A method is presented for predicting base flow using easily measured, or estimated, hydrogeologic parameters. A mathematical model based upon the theory of subsurface flow to parallel drains is applied to a small watershed in Oklahoma. An example of model application is presented for a five-year period of record from this small watershed. Three years of data are used to calibrate the model, and two years of data are used for model validation. Hydrographs of observed and predicted base flow are presented for the five-year period of record. We concluded from this limited application of the model, on a small watershed, that the modeling techniques discussed herein were valid and should be tested for longer time periods on a larger watershed to determine their general applicability.     

HYDROLOGIC EFFECTS OF THE FLOOD ABATEMENT PROGRAM IN SOUTHWESTERN OKLAHOMA1

ABSTRACT: Winter Creek is a tributary of the Washita River in south-western Oklahoma. The Soil Conservation Service installed floodwater retarding structures which controlled runoff from 56 percent of a 33-square-mile (8550-hectare) gaged drainage area. Application of a hydrologic model to the flood peaks indicated that the structural treatment reduced the flood peaks an average of 61 percent. The Winter Creek channel has narrowed and deepened since the structural treatment was applied. The severe bank erosion occurring before treatment has been arrested and sediment yield from the watershed has been reduced 50 to 60 percent. In some reaches of the channel there has been a dense growth of trees in recent years.     

OPTIMIZING THE RETURN FROM A JOJOBA PLANTATION UNDER SCARCE DATA CONDITIONS1

ABSTRACT: There is a serious shortage of yield data for Jojoba (SIMMONDSIA CHINENSIS) from mature and cultivated plantations of ten years or older. Thus, the optimal quantities of water and fertilizers that are needed annually by a Jojoba plantation to achieve maximum profits were estimated from existing plantations. A computer model (IMSL subroutine ZXMWD) was used to determine a Mitscherlich yield function. An economic profit model that incorporates the yield function was then designed to maximize the profits. According to the net present value (NPV) criterion, the maximum yearly net profit is about $7800 per ha, which is achieved during the 11th growth year. The computed cumulative NPV is approximately $21,000 per ha for the entire 15-year period. Similar profits were calculated when the model was tested to examine the NPV using different assumptions with respect to varying costs.     

DETERMINATION OF UNGAGED TRIBUTARY FLOWS AND INTERSEGMENTAL RESERVOIR FLOWS USING SPREADSHEET SOFTWARE1

ABSTRACT: Spreadsheet software was utilized on two related large scale trial and error problems. Gaged streamflow data and known reservoir volumes were used to construct a daily continuity balance in order to estimate the daily mean flows from ungaged portions of a study watershed over one year. Watershed yield coefficients were determined for two diverse types of watersheds with and without significant ground water contribution. Subsequently, a spreadsheet template was devised to ensure than an EPA supported water quality model, WASP, would successfully model the actual segmental volumes of a flood control reservoir. Inlet, outlet, and intersegmental advective flows were determined on a two week average basis using a continuity balance, segmental routing, and known segmental volumes. The protocols described relate the use of microcomputers to the resolution of hydraulic and hydrologic problems requiring iterative solutions.     

有机肥施用量与蔬菜硝酸盐和重金属关系初探

为控制施肥对蔬菜和土壤的负面影响,探讨蔬菜合理的有机肥施用量,在不同质地土壤上,田间试验小白菜、苦瓜、豇豆三种蔬菜施不同量有机肥,收获时测定其产量、品质、硝酸盐、重金属及试验前后土壤有机质含量。结果表明,(1)在施适量无机NPK的条件下,每造蔬菜的有机肥施用量(禽畜粪便,下同),砂土上小白菜为4500kg/hm2、苦瓜和豇豆为3000kg/hm2;壤土上,小白菜和苦瓜均宜施3000kg/hm2,豇豆则宜施4500kg/hm2;粘土上,小白菜每造只宜施1500~3000kg/hm2的有机肥。(2)有机肥必须与无机肥合理配合施用,才能获得最佳的产量和品质效果,在砂土上有机肥施得越多,蔬菜的硝酸盐含量越高,其它土壤也有类似趋势。(3)施高量(7500kg/hm2)有机肥的小白菜重金属含量最高,其次是施中量(3000kg/hm2)有机肥的,尤其是Cd。(4)施有机肥3000~4500kg/hm2 适量无机肥可使土壤有机质水平保持在种植蔬菜前的含量水平,该施肥量和方式不仅可使蔬菜高产、优质,还有利于保护土壤肥力。     

乳源优质白肋烟因土施肥技术研究

通过田间试验，研究乳源县砂泥田和红火泥地氮、磷、钾养分的供应特性；白肋烟各生育期吸收氮、磷、钾养分的规律，以及在不同类型的土壤上氮、磷、钾肥的不同配比对白肋烟产量和质量的影响。根据试验结果进行统计，提出了优质白肋烟因土施肥技术方法。     

杂交水稻高产稳产施肥技术研究——Ⅰ.施肥量研究

本文研究了高产杂交水稻的施肥量,通过回归分析建立的土壤养分自然供给量与土壤速效养分含量之间的双曲线方程和水稻产量与养分吸收量之间的幂函数方程,阐明了土壤养分自然供给量随土壤养分含量的变化而变化的规律和水稻产量与养分吸收量之间的关系。同时,介绍了根据土壤养分含量测定值和由这两个方程演算而得的值,运用公式计算水稻计划产量的施肥量的方法,为高产水稻的计量施肥提供了参考依据。     

高铁酸钠电化学合成条件的研究

利用含铁材料为阳极，铜为阴极，NaOH溶液为电解液，于隔膜电解槽中电解制备高铁酸钠。探索了该工艺所必需的各种参数和反应条件，确定了隔膜材料，并对Na2FeO4浓度和电流效率的非一致性变化作出了解释。研究结果表明：在阳极距离为1．3cm（极距2．3cm）、阳极电解液浓度为14mol／L，阴极电解液浓度为4mol／L、温度为35℃、电压为8～9V时，电解2h后得到的Na2FeO4浓度为18．7g／L，电流效率为20％。