Method, device, system, and database for estimating causes of poor drainage

Abstract

To provide a technique for estimating causes of poor drainage of land.SOLUTION: A method of estimating causes of poor drainage is provided, involving estimating causes of poor drainage of land based on at least either of concentration of components and a stable isotope ratio of constituent elements in a stagnant water sample collected from a poor drainage location of the land.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method, an apparatus, an apparatus for estimating the cause of poor drainage, and a database. [Background technology]

[0002] Regarding methods for dealing with poor drainage in agricultural fields, the root cause of poor drainage is often unknown through the experience of individual farmers, and depending on the conditions, counterproductive countermeasures may be adopted. A known conventional technique for investigating the cause of poor drainage in fields is to directly investigate the cause by installing soil moisture sensors, groundwater level sensors, etc. to observe the moisture content (Non-Patent Document 1). Another known technique is to indirectly investigate the cause of poor drainage by measuring the physical properties of the soil that cause poor drainage, and the permeability of structures such as underdrains that promote drainage (Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Quantitative evaluation method for field drainage in paddy-converted upland fields based on volumetric water content monitoring, Mochizuki Hidetoshi, 2021, Transactions of the Japanese Society of Irrigation, Drainage and Forestry Engineering 89, 279-290. [Non-patent document 2] Simple diagnosis and restoration method for drainage function of hydrophobic material culverts, Tsukamoto Yasutaka et al., 2016, Japanese Journal of Soil Science and Plant Nutrition 87, 368-372. Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional techniques such as those described in Non-Patent Documents 1 and 2 require the collection and measurement of soil, which requires large-scale soil surveys involving the excavation of numerous large holes, the preparation and relatively long installation time of physicochemical observation equipment such as soil moisture sensors, and are therefore costly. In addition, interpretation of the measurement results may require advanced expertise.

[0005] One aspect of the present invention has been made to solve the above-mentioned problems, and its object is to provide a technique for estimating the cause of poor drainage in land. [Means for solving the problem]

[0006] In order to solve the above problem, one embodiment of the present invention provides a method for estimating the cause of poor drainage of land, which includes a step of estimating the cause of poor drainage of the land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample.

[0007] An estimation device according to one embodiment of the present invention includes an estimation unit that estimates the cause of poor drainage of land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample.

[0008] An estimation system according to one embodiment of the present invention includes an estimation device according to one embodiment of the present invention and a measurement device that measures at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample.

[0009] A database according to one embodiment of the present invention is a database that is referenced to estimate the cause of poor drainage in land, and stores data that associates at least one of the concentrations of components in a stagnant water sample collected from an area of ​​poor drainage in the land and the stable isotope ratios of the constituent elements of the water with the cause of the poor drainage in the land. [Effects of the Invention]

[0010] According to one aspect of the present invention, a technique for estimating the cause of poor drainage in land can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram illustrating an example of a configuration of a main part of an estimation system according to an aspect of the present invention. [Figure 2] 1 is a graph showing the relationship between the dissolved silicic acid concentration and the stable oxygen isotope ratio of water in a stagnant water sample and the cause of poor drainage. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes in detail the embodiments of the present invention. Note that the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0013] [Estimation system] An estimation system according to one embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a block diagram showing an example of the configuration of the main parts of an estimation system 100 according to one embodiment of the present invention. As shown in FIG. 1, the estimation system 100 includes a measurement device 10 and an estimation device 11. The estimation system 100 may also include a display device 20, an input device 30, and a reference database 40. The estimation system 100 may include the measurement device 10, the estimation device 11, and other devices as independent devices, or may be integrated into a single device. The estimation system 100 is a system that measures a water sample collected from a location of poor drainage on land and estimates the cause of the poor drainage on the land based on the measurement results.

[0014] The display device 20 displays the estimation results estimated by the estimation device 11. The display device 20 may also display the measurement results measured by the measurement device 10. The display device 20 may display this information as an image. The display device 20 may also be a display of a mobile device such as a smartphone that displays this information.

[0015] The input device 30 accepts input operations by a user to the measurement device 10 and the estimation device 11. As an example, the input device 30 accepts an input to start estimation processing in the estimation device 11.

[0016] (Measuring device 10) The measuring device 10 measures at least one of the concentrations of constituent elements in a water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water in the water sample. The water sample measured by the measuring device 10 can be surface water that has accumulated on the ground surface of a poorly drained area several days or more after the most recent rainfall, or water collected by digging a shallow hole in a poorly drained area. However, it is preferable that the water to be collected does not contain undecomposed organic matter such as grass plant remains, such as rice straw and rice husks, because this can affect the concentrations of constituents in the water sample. Since acetic acid is the organic acid most commonly produced when undecomposed organic matter, such as rice straw, is present in soil, measuring the acetic acid concentration can eliminate the influence of undecomposed organic matter on the concentrations of constituents in the water sample.

[0017] For example, a method for collecting a stagnant water sample involves inserting a syringe directly into the water surface or ground to draw the stagnant water sample, attaching a filter to the syringe, and transferring the filtered stagnant water sample to a storage container. The filter is used to prevent the infiltration of substances that affect the concentration of the target components, such as soil particles and diatoms, into the stagnant water sample. The filter may be made of any material other than a glass filter containing silica. Furthermore, if the sample location is low in water, a porous clay tube may be attached to the tip of the syringe. The collected stagnant water sample may be stored in a sealed container such as an Eppendorf tube until measurement. Considering the possibility of elution of the target components from the container into the stagnant water sample, polyethylene or other suitable materials are preferred. The volume of the stagnant water sample collected may be approximately 0.6 mL, but the volume may be increased if the sample location has local characteristics or if the possibility of contamination is taken into account.

[0018] <Concentration of components in stagnant water samples> The concentration of a component in a stagnant water sample that is the target of measurement by the measurement device 10 may be the concentration of a solute in the stagnant water sample. One example of a component in a stagnant water sample that is the target of measurement by the measurement device 10 is silicic acid dissolved in the stagnant water sample. In addition, the components in a stagnant water sample that are the target of measurement by the measurement device 10 may include dissolved ions (hydrogen ions, fluoride ions, chloride ions, bromine ions, sulfate ions, nitrite ions, nitrate ions, phosphate ions, bicarbonate ions, sodium ions, potassium ions, calcium ions, magnesium ions, ammonium), dissolved gases (oxygen, carbon dioxide, argon, krypton, radon ( 222 Rn), chlorofluorocarbons (CFCs), sulfur hexafluoride, etc.), metal components (iron, manganese, aluminum), organic matter (pesticidal components, corrosive substances, organic acids), microbial flora, environmental DNA, radioactive isotopes of hydrogen in water, etc.

[0019] It is known that rainwater immediately after precipitation does not contain silica, but that the concentration of dissolved silica gradually increases upon contact with mineral soil layers (Sakuma and Sato, Research Report of the Hokkaido University Faculty of Agriculture Experimental Forest, 1987, Vol. 44, pp. 553-565). This is due to the weathering of rocks by rainwater; the longer rainwater permeates underground and flows through the gaps in the rocks as groundwater, the more weathering progresses, and the greater the amount of silicates, a component found in large amounts in rocks, that dissolves into the water as silicate.

[0020] Therefore, by measuring the dissolved silicic acid concentration in a reservoir water sample using the measuring device 10, it is possible to estimate whether the water at the reservoir water sample collection site is surface reservoir water or groundwater. In other words, if the dissolved silicic acid concentration in a reservoir water sample is low, it is likely that the reservoir water sample is surface reservoir water that has had a relatively short contact time with rocks. Conversely, if the dissolved silicic acid concentration in a reservoir water sample is high, it is likely that the reservoir water sample is groundwater that has had a long contact time with rocks.

[0021] The method for measuring the concentration of dissolved silicic acid in a stagnant water sample using the measuring device 10 may be a conventionally known method, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES) or absorptiometry such as the molybdenum yellow method, in which yellow β-molybdosilicic acid is quantitatively produced by reaction with molybdate, and the absorbance of the resulting product is measured at around 390 nm, or the molybdenum blue method, in which the β-molybdosilicic acid is further treated with a reducing agent to form a heteropoly blue complex, which is measured at around 815 nm.

[0022] <Stable isotope ratios of constituent elements in water samples> The stable isotope ratio of the constituent elements of the water in the stagnant water sample to be measured by the measurement device 10 is, for example, the oxygen stable isotope ratio of the water in the stagnant water sample. Alternatively, the stable isotope ratio of the constituent elements of the water in the stagnant water sample to be measured by the measurement device 10 may be the hydrogen stable isotope ratio.

[0023] It is known that water on the earth's surface evaporates due to temperature rises and other factors, causing broken water molecules to fly out of the liquid water. In this case, water molecules containing oxygen-16, a stable oxygen isotope with a small mass, evaporate first, while water molecules containing oxygen-18, a larger mass, remain in the liquid. In other words, the more evaporation there is, the greater the proportion of oxygen-18 in the water (Hamada et al., Journal of the Japanese Society of Hydrological Sciences, 2004, Vol. 34, pp. 209-216). Here, the stable oxygen isotope δ 18 The O ratio is the deviation of oxygen-18 contained in the target water, expressed in parts per thousand, from the Vienna Standard Mean Seawater (VSMOW).

[0024] Therefore, by measuring the stable oxygen isotope ratio of the water in the stagnant water sample using the measurement device 10, it is possible to estimate whether the water at the stagnant water sample collection site is subject to strong evaporation. 18 If the ratio of O is low, it is likely that the groundwater sample is one that has not been subjected to much evaporation. 18 If the ratio of O is high, the water sample is likely to be surface water that has been subject to strong evaporation.

[0025] The method for measuring the oxygen stable isotope ratio of water in a stagnant water sample using the measurement device 10 may be a conventionally known method, such as a method using a stable isotope ratio mass spectrometer after pretreatment using the carbon dioxide equilibration method, or a method using wavelength scanning cavity ring-down spectroscopy.

[0026] (Estimation device 11) The estimation device 11 includes an acquisition unit 12 and an estimation unit 13. The estimation device 11 estimates the cause of poor drainage of land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample.

[0027] The acquisition unit 12 acquires at least one of the concentrations of components in the stagnant water sample and the stable isotope ratios of the constituent elements of the water measured by the measurement device 10. The acquisition unit 12 may be configured to acquire the measurement results continuously, or may acquire the measurement results at predetermined intervals or when an input to start acquiring the measurement results is received from the user via the input device 30. The acquisition unit 12 outputs the acquired measurement results to the estimation unit 13.

[0028] The estimation unit 13 estimates the cause of poor drainage in the land based on the measurement results acquired by the acquisition unit 12. The estimation unit 13 can estimate the cause of poor drainage in the land from which the measurement results were obtained by comparing the measurement results with existing data stored in a reference database 40 (described later). The estimation unit 13 outputs the estimation result of the cause of poor drainage to the display device 30. The estimation unit 13 may also store data in the reference database 40 that associates the estimation result of the cause of poor drainage with at least one of the measurement results of the concentration of components in the stagnant water sample and the stable isotope ratio of the constituent elements of the water, and update the reference database 40.

[0029] (Reference database 40) The reference database 40 is a database that is referenced to estimate the cause of poor drainage in land. The reference database 40 stores data that associates at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water with the cause of the poor drainage in the land. The reference database 40 may be stored in the cloud or on a server.

[0030] [Method for estimating the cause of poor drainage] An example of an estimation method according to one embodiment of the present invention is a method for estimating the cause of poor drainage using an estimation device 11. The estimation method according to one embodiment of the present invention includes a step of estimating the cause of poor drainage of land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​land and the stable isotope ratios of constituent elements of water in the stagnant water sample.

[0031] As an example of a method for estimating the cause of poor drainage, the cause of poor drainage in a target piece of land is estimated based on the relationship between the dissolved silica concentration and stable oxygen isotope ratio of water in a stagnant water sample collected from land where the cause of poor drainage is known, and the cause of poor drainage. This method for estimating the cause of poor drainage will be described with reference to Figure 2. Figure 2 is a graph showing the relationship between the dissolved silica concentration and stable oxygen isotope ratio of water in a stagnant water sample collected from a poorly drained area of ​​land where the cause of poor drainage is known, and the cause of poor drainage.

[0032] In Figure 2, the x-axis represents the stable oxygen isotope δ in the water of the standing water sample compared to the rainwater. 18 The ratio of O (hereinafter, element δ 18 The Y-axis shows the dissolved silica concentration (hereinafter also referred to as element Si) of the above-mentioned stagnant water sample compared to spring water. As will be described later, the dissolved silica concentration in the stagnant water sample (Sisample) on the Y-axis is a value corrected by the background silica concentration (Sibg). Sibg can vary depending on the geology of the location where the stagnant water sample was collected. The group of plots indicated by O in Figure 2 represents rainwater as a control group, and the element δ 18 Both O and element Si are close to 0.

[0033] The group of plots indicated by A in Figure 2 shows the waterlogged samples in the area of ​​poor drainage due to surface waterlogging. The element Si is close to 0, and the element δ 18 Group O is higher than Group O. In other words, it is a waterlogged sample that is subject to stronger evaporation than rainwater, but the contact time with the rocks is not much different from that of rainwater.

[0034] The group of plots indicated by B in Figure 2 shows the water retention samples in the area with intermediate surface-subsurface drainage problems. 18 Both O and O are slightly higher than those in Group O. In other words, these are waterlogged samples that are subject to stronger evaporation than rainwater and have a longer contact time with rocks.

[0035] The group of plots indicated by C in Figure 2 shows the water-logged samples in the stagnant groundwater type drainage deficiency area. 18 Both O and Si are higher than those in Group O, and Si is even higher than in Group B. In other words, these are waterlogged samples that are subject to stronger evaporation than rainwater and have a longer contact time with rock than those in the intermediate surface-subsurface type of poorly drained area.

[0036] The group of plots indicated by D in Figure 2 shows the stagnant water samples from the poorly drained area of ​​groundwater discharge type. 18 Both O and Si are higher than those in group O, and Si is comparable to that in group C, but δ 18 O is slightly less than Group C. In other words, compared to the stagnant groundwater type poorly drained area, this is a waterlogged sample that has had the same amount of contact time with rocks but has been subjected to less evaporation.

[0037] In this way, based on the concentrations of elements in the stagnant water samples collected from areas of poor drainage on land and the stable isotope ratios of the constituent elements of the water in the stagnant water samples, it is possible to estimate the cause of the poor drainage by referring to which group the plot of the stagnant water sample from that area is closest to. As a result, it is possible to select an appropriate countermeasure depending on the cause of the poor drainage.

[0038] That is, by referring to the graph in Figure 2, the causes of poor drainage on land can be classified as follows: (1) This occurs when rainwater that falls on land pools and accumulates in puddles due to low permeability of the ground surface, preventing it from seeping into the ground (hereinafter referred to as surface water retention type drainage problems); (2) Poor drainage occurs when rainwater seeps into puddles and water flowing from nearby areas remains in shallow areas of the land due to low permeability near the land surface (hereinafter referred to as intermediate surface-subsurface drainage deficiency); (3) Poor drainage caused by rainwater seeping into the ground and stagnating deep in the ground due to low permeability of the land (hereinafter referred to as stagnant groundwater type drainage problems); (4) Groundwater flowing deep in the ground springs up to the surface (hereinafter referred to as groundwater spring-up drainage deficiency).

[0039] For example, when poor drainage occurs in a field where crops are grown, the appropriate countermeasures vary depending on the classification of the cause of the poor drainage. Specifically, (1) in the case of poor drainage due to surface water retention, appropriate countermeasures include field leveling, ridge construction, construction of open culverts, and field plowing to remove puddles. (2) In the case of intermediate surface-subsurface drainage failure, in addition to the same improvements as for surface water retention, groundwater countermeasures such as bullet culverts and rice husk culverts can also be adopted. (3) In the case of poor drainage due to stagnant groundwater, drastic improvements can be made by constructing permanent culverts, or measures such as bullet culverts and rice husk culverts can be used to lower the water level to the root zone of the crops. (4) In the case of poor drainage due to groundwater seepage, drastic improvements involving civil engineering, such as construction of permanent culverts, are required.

[0040] Constructing a permanent underdrain in a field with poor drainage due to surface water retention would not only result in excessive wasteful costs, but also in the potential for further adverse side effects due to disturbances caused by heavy machinery. Furthermore, constructing a framed open conduit in a field with poor drainage due to groundwater seepage would be unlikely to improve drainage. A framed open conduit is a drainage ditch dug 20-30 cm deep along the edge of a field and connected to a drainage outlet in the field. A bullet culvert is a water-flowing hole created 30-60 cm deep in the soil by attaching a bullet-shaped drainer to a tractor and pulling it. A rice husk culvert is a trench cut about 40 cm deep in the field and filled with rice husks to provide water supply to an existing main conduit. A proper culvert is a trench cut into the field to a depth of about 50 cm, with a suction pipe buried in it and the top of the pipe filled with a highly permeable hydrophobic material.

[0041] The method for estimating the cause of poor drainage is to classify the causes of poor drainage as described above based on at least one of the dissolved silica concentration in the stagnant water sample and the stable oxygen isotope ratio of the water, thereby making it possible to select an appropriate countermeasure depending on the cause of the poor drainage.

[0042] Furthermore, the method for estimating the cause of poor drainage may refer to a reference database 40 that associates at least one of the concentrations of components in a water sample and the stable isotope ratios of the constituent elements of the water in land where the cause of poor drainage is known with the cause of the poor drainage in that land, thereby enabling more accurate estimation of the cause of the poor drainage.

[0043] Furthermore, the method for estimating the cause of poor drainage may include adding data correlating the estimated cause of poor drainage in the land with at least one of the concentrations of components in the stagnant water sample in the land and the stable isotope ratios of the constituent elements of the water to the reference database 40. This can improve the accuracy of estimating the cause of poor drainage using the reference database 40.

[0044] Dissolved silica concentrations and stable oxygen isotope ratios in water can vary depending on factors such as the geology, altitude, and distance from the sea (latitude). For example, because silica leaches from rocks, dissolved silica concentrations are strongly influenced by geology. Furthermore, the stable oxygen isotope ratios in water change when seawater, the source of much of the Earth's rainwater, evaporates to form clouds and bring rain to land. Even the newly evaporated clouds contain large amounts of oxygen-18. When the clouds' water vapor turns into rain, the larger water molecules fall to the ground first. This results in a relative increase in the proportion of small oxygen-16 in the cloud's water vapor. When the clouds are subsequently blown inland by wind and become rain again, the stable oxygen isotope ratios in the rainwater change compared to the initial rain. Therefore, the stable oxygen isotope ratios in water are affected by the distance from the sea. Furthermore, the stable oxygen isotope ratios in rainfall differ between low and high altitude locations, which can affect the stable oxygen isotope ratios in water. In addition, seasonal changes in air masses may affect the oxygen stable isotope ratio of water. Therefore, it is preferable that the reference data be collected in the same region and in the same season as much as possible. Alternatively, it may be necessary to make appropriate corrections between the reference data and the data of the location where the cause of poor drainage is being estimated.

[0045] The estimation system 100 can easily estimate the cause of poor drainage from the measurement results of at least one of the component concentrations in a water sample and the stable isotope ratios of the constituent elements of the water. As a result, it is possible to easily investigate the cause of poor drainage in land without installing observation equipment or having specialized knowledge, and to appropriately select a countermeasure.

[0046] 〔summary〕 A method for estimating the cause of poor drainage according to one embodiment of the present invention includes a step of estimating the cause of poor drainage of land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample.

[0047] This allows the cause of poor drainage to be easily estimated from the measurement results of at least one of the component concentrations in the water sample and the stable isotope ratios of the constituent elements of the water. As a result, it is possible to easily investigate the cause of poor drainage in land without installing observation equipment or having specialized knowledge, and to select an appropriate countermeasure.

[0048] In the method for estimating the cause of poor drainage according to one aspect of the present invention, the concentration of a component in the stagnant water sample may be a dissolved silica concentration, which allows the contact time of the stagnant water sample with the rock to be estimated from the dissolved silica concentration, thereby enabling the cause of the poor drainage to be estimated.

[0049] In the method for estimating the cause of poor drainage according to one aspect of the present invention, the stable isotope ratio of the constituent elements of the water in the stagnant water sample may be an oxygen stable isotope ratio, which allows the degree of evaporation experienced by the stagnant water sample to be estimated from the oxygen stable isotope ratio, thereby enabling the cause of the poor drainage to be estimated.

[0050] In one aspect of the present invention, the method for estimating the cause of poor drainage may further include, in the estimating step, a step of estimating the cause of poor drainage in the land by referring to a reference database that associates at least one of the concentrations of components in the stagnant water sample and the stable isotope ratios of the constituent elements of the water in the land for which the cause of poor drainage is known with the cause of the poor drainage in the land. This allows for more accurate estimation of the cause of the poor drainage.

[0051] The method for estimating the cause of poor drainage according to one aspect of the present invention may include a step of adding data correlating the cause of poor drainage in the land estimated in the estimation step with at least one of the concentrations of components in the stagnant water sample in the land and the stable isotope ratios of the constituent elements of the water to the reference database, thereby improving the accuracy of estimating the cause of poor drainage using the database.

[0052] In the method for estimating the cause of poor drainage according to one aspect of the present invention, the estimating step may estimate the cause of poor drainage based on both the concentrations of components in a water sample collected from a poorly drained area of ​​the land and the stable isotope ratios of the constituent elements of the water in the water sample. This allows for more accurate estimation of the cause of poor drainage.

[0053] An estimation device 11 according to one embodiment of the present invention includes an estimation unit 13 that estimates the cause of poor drainage of land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample.

[0054] This allows the cause of poor drainage to be easily estimated from the measurement results of at least one of the component concentrations in the water sample and the stable isotope ratios of the constituent elements of the water. As a result, it is possible to easily investigate the cause of poor drainage in land without installing observation equipment or having specialized knowledge, and to select an appropriate countermeasure.

[0055] An estimation system 100 according to one embodiment of the present invention includes the estimation device 11 and a measurement device 10 that measures at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample. This makes it possible to easily estimate the cause of poor drainage based on the measurement results of at least one of the concentrations of components in the stagnant water sample and the stable isotope ratios of the constituent elements of the water.

[0056] The reference database 40 according to one embodiment of the present invention stores data correlating at least one of the concentrations of components in a water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water with the cause of the poorly drained area of ​​the land. As a result, the reference database 40 can be used to estimate the cause of the poorly drained area. [Industrial Applicability]

[0057] The present invention can be used in the agricultural and civil engineering fields, as well as in any other area where land drainage measures are required. [Explanation of symbols]

[0058] 10. Measuring equipment 11 Estimation device 12 Acquisition Department 13 Estimation part 40 Reference Databases 100 Estimation System

Claims

1. A method for estimating the cause of poor drainage of land, comprising a step of estimating the cause of the poor drainage of the land based on at least one of the dissolved silica concentration as a concentration of a component in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratio of the constituent elements of the water in the stagnant water sample.

2. 2. The method for estimating the cause of poor drainage according to claim 1, wherein the stable isotope ratio of the constituent elements of the water in the stagnant water sample is an oxygen stable isotope ratio.

3. A method for determining the cause of poor drainage of land based on at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample, In the estimation step, the cause of poor drainage in the land is estimated by referring to a reference database that associates at least one of the concentrations of components in the stagnant water sample and the stable isotope ratios of the constituent elements of the water in the land where the cause of poor drainage is known with the cause of the poor drainage in the land.

4. 4. A method for estimating the cause of poor drainage as described in claim 3, further comprising a step of adding data to the reference database that correlates the cause of poor drainage of the land estimated in the estimation step with at least one of the concentrations of components in the stagnant water sample in the land and the stable isotope ratios of the constituent elements of the water.

5. A method for estimating the cause of poor drainage of land based on both the concentration of components in a stagnant water sample collected from an area of ​​the land with poor drainage and the stable isotope ratio of the constituent elements of the water in the stagnant water sample.

6. An estimation device having an estimation unit that estimates the cause of poor drainage of land based on at least one of the dissolved silica concentration as a concentration of a component in a stagnant water sample collected from a poorly drained area of ​​the land and the stable isotope ratio of the constituent elements of the water in the stagnant water sample.

7. The estimation device according to claim 6 ; a measuring device for measuring at least one of the concentrations of components in a stagnant water sample collected from a poorly drained area of ​​land and the stable isotope ratios of the constituent elements of the water in the stagnant water sample; An estimation system comprising:

8. An estimation device equipped with an estimation unit that estimates the cause of poor drainage of land based on both the concentration of components in a stagnant water sample collected from an area of ​​the land with poor drainage and the stable isotope ratio of the constituent elements of the water in the stagnant water sample.

9. A database to be referenced to estimate the cause of poor drainage of land, A database that stores data correlating at least one of the concentrations of components in stagnant water samples collected from areas of poor drainage on land and the stable isotope ratios of the constituent elements of the water with the causes of the poor drainage on the land.

Images