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Technical Tools |  |
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To illustrate the areas of expertise employed by the Company, we have defined twenty-seven 'technical tools' that are employed frequently in the course of providing our services. These are our tools of the trade. In the projects section of this website, each project is cross referenced to the suite of technical tools we have employed, to help illustrate the technical scope of each project. Scroll down to read a description of each tool, or use the navigation form at the top of the page or the menu below to jump to an item of interest.
Water balance analyses describe inflows, outflows and routing of water within the study area typically a field, a canal service area or an entire district. Davids Engineering specializes in operational water balances of irrigated areas that assess how flow paths within the service area (including spillage, seepage, deep percolation, drainage and crop water consumption) interact and influence inflows to and outflows from the irrigated area. Our water balances generally include both surface and subsurface flow paths, are designed to mirror the structure of the irrigation and drainage network within the study area and generally usa a monthly time step over a multi-year period of record. This emphasis leads to a water balance that is a powerful tool for assessing the effectiveness of district operations and identifying opportunities for water management improvements.
Davids Engineering uses various computer modeling techniques to simulate the fate of water in the crop root zone. These techniques estimate infiltration from irrigation and precipitation, changes in the volume of stored water and outflows from the root zone due to crop water use, evaporation and deep percolation. These seasonal or multi-year tracks of water movement are important to determining the effectiveness of irrigation water use and to understanding how destinations such as deep percolation and ET of applied water vary with weather conditions, water supplies, soils, cropping patterns and other factors that influence agricultural water management. Davids Engineering selects the appropriate tool for use in root zone simulation based on the availability of data, the desired time step, and level of detail needed to meet the requirements of the client.
Typically, the biggest source of outflow from an irrigated area is crop ET, and, frequently, this is the source of outflow that is known with the least certainty. Davids Engineering emphasizes comprehensive analysis of ET of precipitation and of applied water to generate the best possible estimates of actual crop ET and the clearest understanding of the effectiveness of irrigation practices. Techniques used to estimate crop ET range from estimates based on time series of local weather and cropping data to use of surface energy balance techniques that rely on satellite imagery. Selection of the appropriate technique is based on the needs of our client, the availability of data and our knowledge of the irrigation management techniques used in the study area.
Analysis of conveyance systems is important for assessing their performance and opportunities for expansion or modernization. Davids Engineering performs computer simulations of canal and pipeline conveyance systems to profile discharge volumes and pressures throughout the system, and to determine parameters central both to design of new systems and to evaluation of existing systems. Our hydraulic analysis supports operational studies of system spillage, seepage and deliveries and simulation of the impacts of structural or operational modifications on system operation, drain discharge and water quality. Hydraulic analyses are most often performed in support of irrigation system modernization efforts.
Accurate water measurement is key to effective water management, however, the resources dedicated to measuring water should be matched with the expected benefits. Davids Engineering approaches water measurement studies by first understanding a water supplier's current capability to measure flows and by assessing the potential costs and benefits that could be attained from more accurate or more comprehensive measurement. For suppliers who could benefit substantially from improved measurement, our studies investigate strategic location of water measurement devices, selection of the appropriate structures and instrumentation for measuring and recording flow, and design and operation of a program to collect, quality control, store and analyze measurement data.
Canal spillage typically occurs at well known locations, but tends to be highly variable with respect to time. Therefore, it is one of the more difficult aspects of irrigation operations to analyze. Davids Engineering's approach to spillage analysis is to analyze available spillage data to identify patterns that may reveal spillage "drivers", recognizing that the drivers include physical and operational parameters. Identification of the drivers that cause spillage may then lead to formulation of the operational changes or facility improvements needed to achieve better spillage control and reduced spillage volumes. Initiatives to reduce spillage are often combined with delivery service improvement and involve application of system automation and SCADA technologies.
In contrast to canal spillage, canal seepage typically varies slowly with time, but in most cases has high spatial variability. Our approach to seepage testing depends primarily on the scope of the lining program. For projects addressing only a few candidate reaches, the preferred approach is to test each reach. For programmatic efforts were the objective is to prevent the largest volume of seepage with the least amount of money, we design strategic seepage testing programs. Such programs involve identification of seepage "drivers", segmenting the canal in reaches according to the identified drivers, and then testing an adequate number of representative reaches to support systemwide estimates through inference modeling. In nearly all cases, ponding tests are the preferred test method. In special cases, inflow-outflow measurement tests can provide satisfactory results.
Davids Engineering recognizes that irrigation water management is becoming increasingly sophisticated, that techniques for measuring and recording flow and water quality data are improving, and that regulatory (or quasi-regulatory) oversight of agricultural water use is increasing. These conditions lead to a growing need on the part of water suppliers to collect, store, retrieve, and analyze data. We have found that the hardware platforms and software applications needed for information management vary among agencies and that the design of the data management approach must reflect the particular water management operations of each district. Nevertheless, although the structure of a centralized information management system must be tailored to the needs and operations of individual districts, the concept of centralized data management is broadly applicable because it enables efficient quality control and storage of data and provides operators and managers access to up-to-date, accurate, and consistent information.
Water resource and agricultural data typically display large temporal and spatial variability due to fluctuations in factors related to climate, system operations, irrigator experience, water quality and economics. Statistical analysis is often used to identify patterns in these types of data, to discern causal factors underlying observed patterns and in preparing water management strategies capable of responding to foreseeable variations in water supply and demand. Our approach to statistical analyses is to identify the physical or behavioral mechanisms that could be the drivers of observed conditions, and then on designing analyses to determine whether correlations between the observed conditions and drivers exist and are statistically significant. This approach leads naturally to insights into the measures that may be applied to improve system performance.
Irrigation and drainage of agricultural lands involves modification of natural hydrologic processes to enable sustainable farming in arid areas. Frequently, productive irrigation and drainage systems conform well to their natural setting because they were designed based on an understanding of native surface water and groundwater conditions. Nevertheless, because agricultural water management does alter natural hydrology, careful analysis of surface water and groundwater hydrology is important for determining how design and operation of irrigation and drainage systems may be improved, for understanding the impacts of irrigated agriculture on local hydrology and in determining how undesirable impacts can be alleviated or mitigated.
Davids Engineering's modeling of reservoir operations typically focuses on storage facilities located within irrigation districts that are used for hour-to-hour or day-to-day system regulation. For these facilities, the challenge is to optimize their intended use for absorbing temporary mismatches between system flow and delivery demand, thereby increasing delivery flexibility while minimizing operational spillage. Operational modeling of these facilities is often accompanied by development and testing of reservoir operating rules and locally controlled facilities automation algorithms. Davids Engineering analyzes historical reservoir inflows, outflows, water levels, spillage volumes and demand patterns in our modeling of reservoir operations.
Geographical information systems provide a powerful tool for analysis of data on land use, soils, climate and other parameters used in the study of irrigated agriculture. These analytical capabilities permit Davids Engineering to study variations within single parameters (e.g., how water use varies among fields mapped as having a single land use) as well as interactions among multiple parameters (e.g., how cropping corresponds with soil type). A particularly powerful use of GIS is to overlay measurements of actual ET or of biomass production generated by satellite imagery onto land use mapping to identify relations between actual ET and various land uses. Davids Engineering uses our expertise in GIS primarily as an analytical tool. A secondary, yet also powerful function of GIS is the capability to produce maps that display both base data and analytical results.
In a general sense, decision support systems are analytical tools designed to support either planning decisions or to support routine operational decision-making. Davids Engineering's experience in the development of these types of tools ranges from sophisticated computer models for program planning, to user-friendly operational models, to guidelines available in print or on the web designed to offer guidance to a large number of potential users. The Vail System Reservoir Decision Support System developed by Davids Engineering for the Imperial Irrigation District is a good example of a practical tool developed to support routine irrigation system operation. In this case the objective was to reduce canal spillage while providing desired levels of delivery flexibility.
Reduction of non-point source pollution from agriculture continues to be an important mechanism for improving water quality. Sound analysis of the impacts of irrigated agriculture on water quality rests on the ability to collect sufficient flow and water quality data to represent conditions in the study area and the ability to analyze these data. Data analysis enables assessment of constituent loadings and concentrations, determination of trends or correlations in the data, and identification of sources of constituent loadings. As a company that focuses on improving irrigated agriculture, Davids Engineering's approach to agricultural water quality is informed by a well-developed understanding of irrigated farming and of the practicality and consequences of various types of water quality controls.
Collection and analysis of water quality data can show relationships useful in water quality modeling. Water quality modeling is particularly useful for predicting the impact changes in irrigation practices may have on constituent loadings and concentrations. Modeling of agricultural watersheds can also be useful in tracing "hotspots" of constituent loading. Water quality modeling of the impact of conservation alternatives on the Salton Sea was key to the modeling effort developed for the EIR/EIS that supported the water transfer between the Imperial Irrigation District and the San Diego County Water Agency.
Davids Engineering applies thorough analyses of cropping, soils, water use and local farming practices to develop conceptual designs for irrigation delivery systems, drainage systems, enhanced wetlands and other features necessary for distribution of irrigation water and collection and treatment of drainage flows. Solid conceptual level designs are crucial for cost estimating and provide clients with clear alternatives for assessment and feedback. Conceptual designs then become the basis for feasibility level designs and final design.
Energy cost and rate analysis are important elements for assessing and controlling the cost of system operation. These analyses are important for design of large, piped distribution systems to optimize the life-cycle costs of construction and system operation. Energy cost analysis is also important in planning studies when assessing rate structures for surface water deliveries versus the cost of pumping groundwater by either the water agency or by individual growers having the option of receiving surface water or pumping groundwater. Finally, understanding agricultural rate structures allows Davids Engineering to advise clients of the options that may be most beneficial to them.
Irrigation system benchmarking is useful in allowing agricultural water suppliers to view how they are performing with respect to key performance indicators. Davids Engineering's approach to system benchmarking is to base the analysis on a careful assessment of the district's facilities and operations. This extensive review conditions the benchmarking on a firm understanding of the context in which the district operates. Because each district's setting and operating practices are unique, this conditioning of the benchmarking reduces the risks of basing comparisons or contrasts on indicators that are, in fact, not equivalent. A water balance analysis often serves as the foundation for system benchmarking.
Davids Engineering develops cost estimates based on conceptual level and feasibility level designs. We rely on standard civil engineering methodologies for cost estimating of civil works and collect information from irrigation districts, equipment suppliers, contractors and other local sources for equipment prices and construction costs of irrigation related facilities where use of standard civil engineering cost guidelines are not appropriate.
Davids Engineering recognizes the importance of clear, decisive project management. Fundamentally, this means delivering the client the product agreed to in the scope of work on schedule and within budget. In addition, because of the nature of many of our projects, project management also entails maintaining close communication with our clients so that as projects evolve or as new information becomes available, we are able to tune project objectives so that they continue to be aligned with the client's needs. Key aspects of project management include formulation of specific work scopes and plans, assigning appropriate technical staff to the project, tracking project costs closely, and, as noted above, clear, timely communication with the client, project participants and interested parties to address both technical and administrative aspects of the project.
Davids Engineering specializes in conducting interviews with growers, system operators and district managers. These interviews provide detailed insights into the functioning of irrigation and drainage systems offered from the population of interviewees. Grower interviews are typically conducted in support of "bottom-up" system modernization planning, so that modernization efforts are founded on a clear understanding of current and future on-farm water service needs. Davids Engineering typically works with staff to identify and select a typical cross-section of growers to be interviewed. We recommend that interviews be deliberately designed to gather the targeted information in a consistent manner, but conducted in an informal, conversational style that puts the growers at ease. The information gathered through interviews helps to reveal both opportunities for system improvement and factors that constrain change. Properly excuted, interviews are a source of valuable information and a means of letting growers know that their needs and opinions are important.
Davids Engineering emphasizes project documentation that is matched with the project needs and client's desires. For comprehensive investigations that will be reviewed by agencies and interested parties, as well as by the client, we recommend production of well-written, complete reports that present technical approaches and results and that support recommendations to the client. A similar approach is recommended for projects that provide the basis for future or ongoing work, such as water balance analyses. For projects conducted completely within a single agency, such as an operations investigation, documentation can often be simplified to the form of a technical memorandum, or condensed project report.
Historically, irrigation districts have focused on system operation and maintenance and on the task of providing reliable, afforable service to their customers. Increasingly, agency managers are viewing their responsibilities as being prudent overseers of the resources under their trust and are looking to exercise this responsibility in ways that go beyond efficient irrigation operations. In some instances, water transfers from agriculture can serve as a tool for protecting an agency's water right while providing revenues to offset rising operations costs. Davids Engineering advises agricultural water agencies on potential strategies for structuring water transfers and in planning district infrastructure to achieve the water conservation or operational flexibility needed to support water transfers. We are well versed with the different types of transfers that are possible, and with the regulatory requirements associated with each type.
Davids Engineering has found that workshops can be used to efficiently distribute information and facilitate decisions, especially decisions by governing Boards or decisions involving multiple parties. Successful workshops require that the right parties are invited to participate, the parties are provided with necessary background information in advance, and the workshop is structured and conducted in a manner that gives adequate attention to all views and opinions. In some cases, workshops should be preceded by "one-on-one" meetings with the participants to identify potential polarizing issues that should dealt with separately.
Davids Engineering staff occasionally provide services in support of litigation or potential litigation, primarily related to quantification of water rights. The conditions under which expert witness work may be taken on include having legitimate expertise in the subject area and being allowed to conduct the investigations needed to adequately develop and support an independent opinion.
Successful design and hosting of tours of international delegates rests on understanding what the visiting delegation hopes to learn during their tour and understanding the background of the delegation. Davids Engineering's approach is to design tours that suit the interests of the delegation and is paced so that the delegates are able to absorb technical presentations and have the opportunity to be exposed to other aspects of American culture of interest to them.
Water management policy frequently rests on technical analyses designed to predict the consequences of various policy options. Therefore, a valuable tool in policy analysis is the ability to perform sophisticated technical analyses that weigh both tangible and intangible factors of policy alternatives and to clearly communicate these findings. Davids Engineering holds the position that policy analysis should be guided by technical considerations, and we take pride in our capacity to describe technical findings in a policy context.
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