Information systems and models for planning water use in land reclamation

Scientific and technical developments in the field of information technologies for water management planning

In Russia and abroad, there are many diverse information systems and models for operational irrigation planning, the actual management quality of which depends on the technical level of communication means, computers, as well as on how accurately the complex of applied models and calculation methods reflects the processes occurring in the fields under specific soil and climatic conditions.

The GNU VNIIGiM of the Russian Academy of Agricultural Sciences has developed a mathematical model for the optimal distribution of water resources in case of their scarcity, which includes a system of mathematical models for operational water distribution planning with a complex hierarchical structure.

The "Programmed Crop Yield System" (PCYS), developed at the main information and computing center of the Russian Academy of Agricultural Sciences, includes a module for calculating soil moisture and irrigation regimes. The initial information contains data on meteorological conditions, precipitation, and plant development stages, based on which, using the water balance equation, the plant moisture supply and the volume of irrigation rates for specific time intervals are calculated.

In 1988, the VNPO "Raduga" developed and implemented a technological service for operational irrigation management (OIM) on on-farm systems with a service area of up to 30,000 hectares.

In 1990, on the irrigation systems of Kazakhstan, the Kazakh Research Institute of Water Management, under the leadership of R.A. Kvan, conducted the development and implementation of the foundations for operational irrigation management and water use organization.

The irrigation management task is solved similarly in the regional irrigation operational planning system developed at the FGBNU "RosNIIPM".

With the help of the ASU OS created in 1990, irrigation management is being implemented for the first time based on a dynamic model of the water regime and agricultural crop yield. In 2002, software and an information-technological support system were developed for irrigation system operation services to manage water use and water distribution processes (Shchedrin V.N., Yanovsky A.S., Kolganov A.V.).

Experimental and industrial verification of methods and software for operational management of irrigation water use on farms, as well as the development and implementation of a methodology for operational planning and adjustment of on-farm water use, were conducted in 1988 (Olgarenko V.I.).

Work on operational irrigation management has been conducted since 1988 by the All-Russian Research Institute for Integrated Automation of Land Reclamation Systems (head of development E.G. Krushel). A complex of tasks for operational water use planning on the irrigation systems of the Crimean UOS in the Krasnodar Territory was considered. Software for task complexes of operational planning and management of technological processes at the level of the Crimean RU OS and Leningrad RPO "Poliv" has been developed.

A complex physical-statistical model developed by M.G. Sanoyan takes into account the growth dynamics of root system and the agrometeorological conditions of moisture exchange in the plant habitat. The solution is based on the functional dependence:

W = Ф (M, L, B), where W is soil moisture reserves;

Ф is the symbol of functional dependence;

M, L, B are, respectively, indicators of meteorological, soil, and biological factors for the calculation period.

This model is a system that combines probabilistic-statistical models, generalizing materials from specially conducted multifactorial experiments, as well as deterministic models describing the physical laws of their parameter formation.

The system of stochastic and deterministic mathematical models by V.V. Shabanov allows assessing the influence of the water and radiation regimes of crops and soil moisture reserves on plant development and determining the design irrigation regime based on solving the water balance equation.

A. Yu. Cheremisinov proposed a model for calculating operational irrigation regimes in the conditions of the Central Black Earth Zone, which allows taking into account the influence of climate factor variability on total evaporation.

V. P. Ostapchik and V.A. Kostromin presented schemes for solving operational planning tasks for irrigation regimes in large irrigated areas using computers. The described complex of models successfully passed industrial verification in the Kiev and Kherson regions of Ukraine and Crimea.

Yu.A. Izrael and O.D. Sirotenko developed the "climate-soil-yield" simulation system.

V.V. Alt (SibFTI) notes in his works the need for the comprehensive development of the use of information technologies in Russian agricultural production.

Similar models are being developed abroad, where significant attention is paid to improving the efficiency of irrigation management. In recent years, a central ISS system has been developed, as well as regional management systems:

• Irrigat
• ISI
• IMS
• CIMIS
• AGMET
• VISP

The models provide for the acquisition of information about field parameters, the cultivated crop, the irrigation system, and general climatic indicators, allowing for the management of irrigation on various types of irrigation systems with different crop rotation structures, taking into account specific soil and climatic conditions.

The information-advisory system for assessing the land reclamation and agrochemical status of irrigated crop rotation plots (FGU "Management Saratovmeliovodkhoz", IAS "Uchastok") is designed to assess the status indicators of reclaimed lands in the Volga region at the least developed local level for individual irrigated fields of a farm, based on the principles of geospatiality and complexity.

Space monitoring and GIS: how to assess the state of a field from above

For effective irrigation management, an agronomist needs up-to-date information about all plots of the farm. Today, this task is solved by geographic information systems (GIS) and remote sensing data. They allow for moving away from approximate calculations and planning irrigation based on the actual condition of the soil and plants.

At the level of a specific field, the situation is assessed by the information-advisory system (IAS) "Uchastok". The program analyzes qualitative agrochemical and land reclamation soil indicators and selects optimal conditions for growing field crops. Due to format compatibility, data from this system is easily integrated with regional GIS-monitoring databases.

• IAS "Uchastok" database — 14 relational files
• System file format — dBase IV
• Start of active GIS development — 1987

Space imagery is indispensable for precision farming, where constant monitoring of the growing season is essential. Agricultural crops in space images are not hidden by other objects, grow in a single layer, and are perfectly deciphered. This gives agronomists the opportunity to instantly react to any deviations in plant development over large areas.

Remote sensing methods are currently being actively applied in the agro-industrial complexes of the USA, Canada, EU countries, India, and Japan. In Russia, the development of a similar system is underway within the framework of the State Program for Agricultural Development. The domestic space system will allow for centralized monitoring of agricultural lands.

Irrigation planning: how to calculate the irrigation rate

Regulation of the water regime is a search for a balance between high crop productivity, water saving, and environmental safety. Irrigated farming is more difficult to subject to mathematical calculation than other technological processes in plant cultivation. Water consumption is constantly changing under the influence of many factors.

The complexity of irrigation planning is due to the following reasons:

• strong dependence on soil and climatic conditions and random weather factors;
• a high degree of irretrievable water use;
• dispersion of water consumers over large areas;
• irregularity of water consumption over time and the need to coordinate irrigation with the needs of the crops.

To maintain soil moisture in an optimal range and save resources, operational information is required. Modern mathematical modeling allows for the automation of this process. To calculate control actions in the field, computer systems need objective data on a number of indicators:

• actual precipitation;
• irrigation regimes;
• dynamics of moisture evaporation;
• features of moisture exchange in the aeration zone;
• agroclimatic conditions and soil moisture reserves.

Methods that account for climate via mean daily air temperature, air humidity, radiation balance, total radiation, and day length have become widely used. These data allow for the automation of calculations. However, in practice, the mathematical model must be adapted to the conditions of a specific field.

Why irrigation regime calculations result in an error of up to 30%

When planning irrigation, agronomists often encounter the fact that theoretical calculations do not match the actual soil moisture. Insufficient accuracy of empirical parameters in calculation formulas leads to errors in irrigation rates of up to 30%. Traditional methods for assessing optimal moisture levels do not take into account how the reduction in soil moisture slows down the evaporation process.

Most of the used methodologies are based on water and heat balance equations. The problem is that the empirical coefficients in these equations are assumed to be constant values. In reality, they change as the moisture availability of the field changes. Furthermore, the formulas cannot reliably account for the crop development stage and the specific features of its water consumption at different moisture levels of the root zone.

At different stages of growth, excess or deficit of moisture affects biomass gain and evaporation intensity in different ways. When soil moisture reserves are low, the crop’s water consumption naturally decreases, while under optimal conditions, calculation methods yield satisfactory results. To increase accuracy, it is necessary to assess exactly how a crop's water requirements change throughout the season.

• Limit error in irrigation regime calculations — 30%
• Difference between evaporation and evaporability in different years — from 10% to 30%

Biological curve method: how to account for development stages and climate

The use of biological curves (or crop biological coefficients) is considered the most well-founded method for regulating irrigation. It links weather conditions, soil moisture reserves, and plant development characteristics. Plotting such curves based on experimental data is carried out in two stages.

1. A family of curves representing the dependence of biological coefficients on soil moisture is constructed separately for each phase of plant development.
2. Based on the obtained data, final curves are plotted, the maximum ordinates of which reflect the dynamics of crop water consumption during ontogenesis.

Under ideal conditions, such curves should be universal for a crop. However, in practice, biological coefficients become zonal (bioclimatic) and change depending on time and territory. For example, an assessment of their variability in arid conditions shows that in dry years, the air humidity deficit grows much faster than total evaporation. The direct linear relationship between them is disrupted.

The main difficulty in calculations lies in the unpredictable combination of temperatures and air humidity deficits in different years, even during the same growth phase. Furthermore, accuracy is affected by significant climate variability by decades and errors in field measurements. For this reason, any empirical formula for calculating irrigation remains strictly regional and works effectively only in the natural conditions for which it was developed.

To increase the stability of variation coefficients and calculation accuracy, it is proposed to use relative indicators that reflect the nature of water consumption in accordance with:

• plant development rhythms;
• changes in climatic factors in their complex interaction.

Sh. Ugrekhelidze proposed an equation that takes into account the change in biological curve coefficients considering the biological characteristics of crops, soil conditions, soil moisture, and major meteorological factors.

Changes in bioclimatic coefficients by zone and over time introduce an element of uncertainty when choosing their value for calculating water consumption using the bioclimatic method. Factors determining their value include:

• crop yield;
• soil fertility;
• level of applied agrotechnics;
• irrigation technique.

Studies by E.A. Strunnikov confirm the variability of bioclimatic coefficients, described by a power-law dependence, with the exponent changing from zero to one. The variability of bioclimatic coefficients, both spatial and temporal, is explained by a number of reasons: the creation of a peculiar microclimate within the plant environment, the dynamics of evaporation from the soil at different moisture levels, the features of the evaporation process in contrasting climatic zones, and sharp weather changes in the same climatic zone. In order to increase the accuracy of calculations for various soil-climatic conditions, it is necessary to calculate a family of regional water consumption curves for major crops. Of significant importance here is the study of patterns in the variability of biological coefficients over time, since weather conditions in individual climatic zones of the country have sharp fluctuations in time and space.

According to V.P. Ostapchik, the main reason for the spatial variability of the coefficients is the unreliability of source data, spatial variability of moisture reserves, precipitation, moisture exchange between the active layer and underlying layers, the degree of dryness of the surrounding territory, failure to account for evaporation spikes after irrigation, and the use of a proportional relationship between evaporation and air humidity deficit. Improving the methodology could involve using coefficients that account for the influence of factors such as wind speed, soil moisture, evaporation spikes, and the size of irrigated fields on evaporation.

V.B. Mestechkin established that biological coefficients (Kb) follow geographical zonality, decreasing with increasing climate aridity from 0.7 to 0.2. Using fixed sets of biological coefficients for calculating water consumption in soil-climatically heterogeneous regions leads to errors reaching 50%. To avoid such errors in regions for which there is no experimental data, spatial interpolation should be used in calculations, the methodology for which is developed depending on the sums of air humidity deficits.

M.G. Golchenko and V.I. Vikhrov refined the bioclimatic model of water consumption, taking into account the non-linear relationship, as well as wind speed, increased evaporation, and changes in yield based on the hay cuts of perennial grasses. In this case, the deviations of the calculated values of total evaporation from the measured ones did not exceed 12.4%.

It has been established that the value of bioclimatic coefficients, corresponding to the air humidity deficit and evaporation from the water surface, increases when moving from southern regions to northern ones. Differences in the level of soil moisture lead to different values of bioclimatic coefficients even in an area with identical climatic conditions. Therefore, in order to increase the accuracy of calculations, it is proposed to differentiate coefficients by climatic zones, taking into account the moisture supply of the crops.

Bioclimatic coefficients reflect the influence of two factors on water distribution: biological development rhythms and meteorological conditions. The dependence of bioclimatic coefficients on weather conditions is established by the deviations of the actual values of bioclimatic coefficients and average daily air humidity deficits from their mean values. It has been established that bioclimatic coefficients depend on the yield level.

S.A. Yakovlev proposed transitional coefficients that allow obtaining the value of water consumption in years with different moisture supply based on the characteristics of changes in long-term average calculated water consumption rates. These values represent the ratio of water consumption values in a given year to the water consumption value in an "average" year in terms of supply.

A model of bioclimatic coefficients for calculating operational irrigation regimes in the conditions of the Central Black Earth zone was proposed by A.Y. Cheremisinov. It is based on the bioclimatic method, refined by taking into account the variability of bioclimatic coefficients depending on the variability of meteorological conditions. Information on air temperature and humidity, the type and development phase of agricultural crops, and moisture supply of the crops is used for the calculation; the average relative error of the calculations is + 10.7.... + 14.2%.

In a number of models, to improve the accuracy of calculations, the influence of crop moisture supply on total evaporation is taken into account, and this dependence is assumed to be linear. The authors believe that differences in the level of soil moisture influence the value of total evaporation even under identical climatic conditions. Therefore, the refinement of the calculation methodology comes down to assessing the influence of crop moisture supply on biological coefficients and total evaporation.

A.I. Mikhaltsevich and A.E. Zhukov proposed a model for calculating total evaporation that allows taking into account the influence of soil moisture content and the development phase of agricultural plants.

The methodology for calculating crop water consumption (author L.G. Balayev) allows for different levels of yield and moisture, as well as the non-linearity of the relationship between total evaporation and climatic factors. In addition, it allows calculating total evaporation for specific climatic, soil-hydrological conditions of the region and biological characteristics of agricultural crops.

Y.F. Dushatkin confirmed that the ratio between evaporation from a water surface (Ew) and total evaporation (ET) from an irrigated field depends on soil moisture reserves. The relationship between Ew and ET is linear up to a certain critical value of soil moisture (WKp), above which it becomes curvilinear.

Similar models are being developed abroad, where great attention is also paid to issues of improving irrigation management efficiency.

In recent years, a centralized ISS system has been developed, as well as regional management systems: Irrigat, ISI, IMS, CIMIS, AGNET, VISP. The models provide for obtaining information on the water-physical properties of the soil of the irrigated field, the cultivated crop, the type of irrigation system, and hydrometeorological conditions. Information-advisory systems for irrigation management allow planning irrigation on irrigation systems taking into account the features of the crop rotation structure, specific soil-climatic and weather conditions. Using the equations of H.B. Blaney-W.D. Criddle, Priestley-Taylor, H.L. Penman, and L. Turc, systems have been developed that make it possible to determine potential evapotranspiration, soil moisture deficit, and optimize the irrigation regime of agricultural crops based on comprehensive information about meteorological, soil, and agronomic conditions.

For the listed models, the basic information includes the name of the farms, the code of the cultivated crop and plot, sowing dates, the efficiency of irrigation equipment, and the maximum reserves of available moisture in the root zone of the soil. Meteorological information contains data on solar radiation, air temperature and dew point, wind speed, air humidity deficit, etc.; current information includes data on the date of the previous irrigation, the permissible decrease in moisture reserves during the given phase of the crop's growing season, the date of the last rainfall during the calculation period, and the amount of moisture received from precipitation and irrigation during the period under consideration.

In the authors' opinion, one of the significant drawbacks of calculation methods is the lack of quantitative information on the influence of crop moisture supply on total evaporation.

Under real production conditions, with high costs for material, technical, and energy resources, as well as environmentally friendly irrigation regimes, maintaining the soil moisture of the root zone at an optimal level is not always considered feasible or possible. In this regard, the same plant development periods can occur in different years under varying moisture supply conditions. To increase the accuracy of calculating total evaporation in such cases, it is necessary to account for its depression under insufficient moisture supply.

Thus, the analysis and research results of the FGBNU VNII "Raduga" provide an opportunity to formulate a concept stating that only the development of calculation methods using comprehensive information on meteorological, soil, and hydrogeological conditions, biological characteristics of crops, and soil moisture, combined with the application of statistical analysis laws and probability theory to assess the nature of the variability of hydrometeorological factors, can serve as a practical basis for the rational organization of irrigation management, ensuring high efficiency and environmental safety of irrigation technologies.

The basic principles for improving irrigation planning methodology consist of the following provisions.

Rationalizing water consumption in agriculture is one of the most important problems, as the use of unjustifiably high irrigation rates leads to a disruption of the water regime and hydrochemical balance, additional feeding of groundwater, its rise, the leaching of mineral and organic compounds from the soil, and the degradation of the ecological situation. To ensure the rational consumption of irrigation water during irrigation, an accurate determination of the degree of moisture supply for a specific field is required. This allows for the timely scheduling of the next irrigation, monitoring of soil moisture reserves, water expenditure on harvest formation, and prevents unproductive losses through surface and deep runoff.

2. Irrigation regime management boils down to determining the soil moisture reserves of the irrigated area at the beginning and end of the calculation period. While the instrumental determination of precipitation and meteorological indicators is quite accessible, the instrumental determination of soil moisture cannot provide the volume of information necessary for the mass adjustment of irrigation regimes. Therefore, changes in soil moisture reserves are determined using the water balance equation with the calculation of total evaporation based on mathematical models.

The main requirements for the models lie in the need to sufficiently and accurately reflect changes in the moisture regime of crops. Adjustment parameters should include data amenable to statistical analysis methods, which can be obtained through mass observations by water balance and agrometeorological stations, and the simplicity of their implementation.

Any computer program for irrigation management works effectively only when accurate input data is incorporated into it. To build a reliable mathematical model, it is important to correctly select the parameters that describe the movement of moisture in the soil. It is necessary to know how the water regime of crops changes with fluctuations in weather, changes in irrigation rates, and the water supply scheme to a specific plot.

The accuracy of calculations depends on two indicators: total evaporation and moisture exchange in the aeration zone. Moreover, the relationship between a lack of soil moisture and a decrease in evaporation is non-linear. Plants at different development phases react to water deficit differently, and this variability must be converted into accurate mathematical dependencies.

Traditional field experiments do not allow for separating the biological characteristics of a crop from the influence of weather, as meteorological conditions during the research are superimposed on the plant development phases. To solve this problem, an improved field experiment methodology is needed. It must show exactly how bioclimatic coefficients change as weather changes.

What needs to be investigated for accurate modeling

For mathematical models to provide an agronomist with accurate recommendations for irrigation management, field research followed by statistical analysis is required. Experiments should solve the following tasks:

• Quantitatively assess how weather and the soil water regime affect total evaporation and crop yield.
• Obtain accurate data on the intensity of moisture exchange in the aeration zone and the structure of the crop water balance under various meteorological conditions.
• Study the structure of the heat-energy balance of crops to accurately assess the influence of weather at different plant development phases on total evaporation and harvest formation.