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1.
Jin-Ah Kim Sang-Woo Lee Gil-Soon Hwang Soon-Jin Hwang Chulgoo Kim Kyung-Jin An 《Paddy and Water Environment》2016,14(2):299-312
Urban land use can adversely affect the water quality of adjacent streams through interactions at the edges of the two ecosystems. From a landscape ecological perspective, edges control the flow rate of materials between two adjacent systems. Based on the rationale that the streamline complexity formed between land uses and water bodies may function in this manner, we investigated the potential role of streamline complexity in the relationship between stream ecological communities and urban land use in Korea. Various indices of biological indicators including the diatom assemblage index for organic pollution, the trophic diatom index, the Korean saprobic index, and the index of biotic integrity were applied at 80 sampling sites in the Nakdong River system. We computed the fractal dimensions of the streamlines within 1-km buffers and the proportion of urban land use in the watershed within 5-km buffers around the sampling sites. A moderation model was adopted to investigate the role of streamline complexity in the relationship between urban land use and the biological indices of ecological communities. A comparison between a simple geometry regression model and complex geometry models indicated that streamline complexity may moderate the adverse impacts of urban land use on ecological communities in streams. The moderating effect of streamline complexity was particularly significant for assemblages of macroinvertebrates and fishes. Therefore, to enhance the ecological integrity of streams, we strongly recommend considering streamline complexity when restoring channelized streams in developed areas. 相似文献
2.
Kim Jinah An Kyung-Jin Hwang Soon-Jin Hwang Gilson Kim Dong-Oug Kim Chulgoo Lee Sang-Woo 《Paddy and Water Environment》2014,12(1):157-168
Numerous studies have stated that land use in urbanized areas can adversely affect water quality of streams. Previous studies reported that edges may play important roles in controlling flow rate of material in two systems. In this study, we examined the mediating effects of streamline geometry on the relationships between urban land use and the index of biological integrity (IBI) of the Nakdong River in Korea. Two mediation models with streamline geometry, including the partial mediation effect model and the full mediation effect model, were estimated to explore the mediating effect of streamline geometry. To measure streamline geometry, we calculated the fractal dimension of a streamline within a 1 km buffer from the sampling sites. The proportion of urban land use within a 5 km buffer of the sampling sites was also computed by GIS. We used biological assessment data from the National Aquatic Ecological Monitoring Program in Korea to delineate the IBI at the sampling sites. The results showed that urban land use significantly degraded stream morphology and IBI in the Nakdong River. It was also observed that streamline geometry mediated the influence of urban land use on the IBI. The results of structural equation modeling analysis for the two mediation models with the fractal dimension and IBI suggested that only two paths were significant in the partial mediation model, whereas all paths were significant in the estimated full mediation model. 相似文献
3.
Seong-Joon Kim Hyung-Joong Kwon In-Kyun Jung Geun-Ae Park 《Paddy and Water Environment》2003,1(3):149-155
The simulated streamflow from Thiessen average rainfall (T) and spatially distributed rainfall (R) may be significantly different from each other. To identify the hydrologic effects quantitatively, the grid-based kinematic wave storm runoff model was adopted. The model predicts temporal and spatial variations of surface and subsurface flow at each cell by calculating the water balance, and routes the streamflow to the outlet. The model was tested at the Yeoncheondam watershed (1,875 km2), one third of which belongs to North Korea. The watershed is elongated to north and south directions crossing the border. Four rain gauges cover the watershed within the territory of South Korea, while no records from North Korea are given. The simulated results showed the large differences in runoff volume and peak flow rates between T and R when rain moves in a north to south direction. The simulated results of east-to-west-direction storms showed little difference in the hydrographs. The hydrograph was strongly affected by the spatial variations of the rainfall moving along the stream of the watershed. 相似文献
4.
In order to prove a reduction function concerning flood damage according to land use, we have to compare evaluation indices,
such as flood concentration times. These can be derived from the calculation of the outflows from two basins where rainfall,
geology, geographical conditions, etc. are the same and only the land use is different. However, it is very difficult to obtain
comparable data from large basins under the above mentioned conditions. An elaborate observation for a long period is required
to obtain such data. In this paper, we aim to establish a calculation process that offers consideration factors from a viewpoint
that is different from a conventional research where elaborate observation is essential. Therefore, first we use easily obtainable
data of many basins, such as the information on the Internet, or data from official documents or the like, which are difficult
to deal with in hydrology. Then, we obtain several evaluation indices, which are coefficients close to the flood concentration
times in this paper, on each basin in which various kinds of land uses are mixed. We then perform the statistical analysis
with a land use ratio. In order to use various data on several basins, we evaluate the difference in the land use ratio in
the basin by using of a length of a riverside instead of an area in the basin. Moreover, since a river-mouth is at the end
of the riverside and a water stage observation point is not at the river-mouth, an error arises. Although there are several
problems in accuracy as mentioned above, the evaluation of the reduction function concerning the flood damage according to
land use will be feasible, automatically and efficiently, if the calculation process is established. 相似文献
5.
The Total Maximum Daily Load (TMDL) program is an integrated process of watershed assessment and management to address surface
water quality impairment. The management of organic contaminants and nutrients is a primary concern in conserving surface
water bodies. Watershed-scale pollutant loads simulation can assist stakeholders and watershed planners in making decisions
on immediate and long-term land use schemes to improve water quality. However, the behavior of contaminants in a watershed
needs to be characterized prior to such model applications. The objectives of this study were to characterize point and nonpoint
pollutants runoff at a watershed scale and to develop a Pollutant Load Calculation Model (PLCM), which facilitates the estimation
of pollutant delivery to a watershed outlet. The developed model was applied for the six sub-watersheds of the Saemangeum
estuarine watershed in Korea, where a large tidal reclamation project has been underway. Two years stream flow and water quality
data were used for the model calibration, while 1 year data were utilized for the model validation. The model calibration
resulted in the R
2 values of 0.58, 0.53, and 0.35 for BOD, TN, and TP, respectively. Overall performance for the validation period was similar
with that for the calibration period although the R
2 values were slightly decreased. The PLCM tends to substantially under or overestimate delivery pollutants loads during the
summer rainy seasons when most rainfall events occur. This is probably because once-a-month-measured water quality data, which
might not represent appropriately monthly water quality, particularly, for rainy seasons, were used for the loads calculation.
Thus, more frequently monitored water quality data should be used for the delivery loads estimation at least for a rainy season
in order to improve the PLCM performance. Nevertheless, the developed model took the pollutant reduction process into account,
which is not allowed with the conventional unit loading method, and furthermore temporal variations of pollutant loads based
on stream flows were also incorporated into the pollutant loads estimation. The developed PLCM can be a useful tool to assess
pollutants delivery loads at a watershed scale and thus assist decision makers in developing watershed pollution management
schemes. 相似文献
6.
South Korea is located in the Asian monsoon region, and paddy rice farming is one of the important agricultural activities,
which may contribute to the non-point source pollution of inland water bodies along with rainfall runoff. The status of water
quality in rural streams located throughout South Korea was examined in this study by water quality monitoring and statistical
analysis. Totally six surveys were conducted in 2003 and 2005 to monitor 300 streams located in rural subwatersheds; these
streams are affected by agricultural activities and water supply for agricultural practices. The monitoring was performed
at the terminal point of each subwatershed. In each study year, the streams were monitored in the three hydrological periods
(April, July, and October) to observe differences in the impacts of agricultural activity and rainfall pattern. During the
surveys, 15 water quality parameters were measured and interpreted using multivariate statistical methods including factor
analysis and cluster analysis. Results show that the water quality of the rural streams monitored in this study appeared to
meet the Korean water quality criteria for agricultural use, which are 8.0 and 100 mg/L for biochemical oxygen demand and
suspended solids, respectively. In terms of organic contamination and suspended solids, the best stream water quality was
observed in October compared to other periods. This can be attributed to the fact that October follows the rice-harvesting
period and has low rainfall; thus the streams are probably less affected by agricultural activities and surface runoff. The
three hydrological periods did not show much variation in the nitrogen and phosphorus parameters related to stream water nutrient
conditions. Factor analysis indicates that the first five factors for April explained about 67% of the total sample variance.
In July, the first four factors explained about 60% of the total variance, while the first four factors for October explained
about 65%. Cluster analysis reveals that the streams could be divided into four groups in April and October and five groups
in July. The box-and-whisker plots of the physicochemical variables indicate that Group A had the best water quality among
the groups. This study demonstrates that the rural stream water quality of South Korea in the Asian monsoon region can be
greatly affected by agricultural activities such as paddy rice farming and rainfall patterns. 相似文献
7.
Pedro Henrique Monteiro do Amaral Lidimara Souza da Silveira Beatriz Figueiraujo Jabour Vescovi Rosa Vívian Campos de Oliveira Roberto da Gama Alves 《Journal of insect science (Online)》2015,15(1)
Insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are often used to assess the conditions of aquatic environments, but few studies have examined the differences in these communities between riffles and pools. Our objective was to test whether riffles shelter greater richness and abundance of EPT, as well as to assess the sensitivity of these insects for detecting impacts from different land uses in streams in southeastern Brazil. Samples were collected in the dry season of 2012 with a Surber sampler in riffles and pools of nine streams (forest, pasture, and urban areas). Principal component analysis distinguished the streams according to different land uses as a function of percentage of plant cover and water oxygenation level and showed partial distinction between riffles and pools as a function of current speed and percentage of ultrafine sand. Detrended correspondence analysis indicated the distinction in EPT composition between riffles and pools, except in urban streams. The results of this study confirm the expected differences in the EPT fauna structure between riffles and pools, especially in forest and pasture environments. The individual metrics of riffle and pool assemblages showed significantly different responses to land use. Therefore, we suggest individual sampling of riffles and pools, since the metrics of these assemblages’ insects can differ between these habitats and influence the results of assessments in low-order streams. 相似文献
8.
Analysis of urbanization characteristics causing farmland loss in a rapid growth area using GIS and RS 总被引:5,自引:0,他引:5
This study aims to analyze the spatial characteristics of urbanization in a rapid growth area. Remote sensing (RS) and geographic information system (GIS) techniques were used to classify land uses in 1986 and 1996, the most rapid growth period. The two land-use maps were classified with accuracies of 90% and 86% in verification areas for 1986 and 1996, respectively, by a supervised maximum likelihood method. Urbanization in the greenbelt within the study area was restricted, while outside the greenbelt it occurred rapidly. Fifty seven percent of the total increase in built-up area in the study area was concentrated in a 10-km GIS-defined buffer zone adjacent to the greenbelt. The priority for new residential development was put on areas with slopes of less than 15 degrees and potential farmland in the areas surrounding Seoul. In the priority area, farmland loss was very significant. These results show that although the environmental protection of ecologically valuable land was well enforced by the greenbelt from urbanization, farmland was not conserved in comparison to new residential development in the rapid growth area. 相似文献
9.
Le Van Chinh Haruka Iseri Kazuaki Hiramatsu Masayoshi Harada Makito Mori 《Paddy and Water Environment》2013,11(1-4):97-112
In watershed management, the determination of peak and total runoff due to rainfall and prediction of pollutant load are very important. Measurement of rainfall runoff and pollutant load is always the best approach but is not always possible at the desired time and location. In practice, diffuse pollution has a complex natural dependence on various land-use activities such as agriculture, livestock breeding, and forestry. Estimation of pollutant load is therefore essential for watershed management and water pollution control. In this study, a model of rainfall runoff and pollutant load, which uses a geographical information system (GIS) database, is a convenient and powerful tool for resolving the abovementioned complexities. This technology was applied in order to simulate the runoff discharge and the pollutant load of total nitrogen (TN) and total phosphorus (TP) in the Chikugo River basin of Kyushu Island, Japan. First, a hydrologic modeling system (HEC-HMS) and GIS software extension tool were used for simulations of elevation, drainage line definition, watershed delineation, drainage feature characterization, and geometric network generation. The spatial distributions of land cover, soil classes, rainfall, and evaporation were then analyzed in order to simulate the daily runoff discharge at the Chikugo Barrage from April 2005 to December 2007. An important point in this approach is that a new development for data input processing with HEC-HMS was introduced for optimizing parameters of the model. Next, the water quality indicators TN and TP were examined, and an efficient approach was investigated for estimating monthly pollutant loads directly from unit load and ground-observed hydrological data. Both nonpoint and point sources of pollutants were considered, including different land-cover categories, sewers, factories, and livestock farms. The observed and simulated results for the runoff discharges and pollutant loads were in good agreement and totally consistent, indicating that the proposed model is applicable to simulation of rainfall runoff and pollutant load in the Chikugo River basin. Further, this model will be able to provide managers with a useful tool for optimizing the water surface management of this river basin. 相似文献
10.
Fatemeh Rajaei Abbas Esmaili Sari Abdolrassoul Salmanmahiny Majid Delavar Ali Reza Massah Bavani Raghavan Srinivasan 《Paddy and Water Environment》2017,15(3):541-552
Pasture, forest, and farmland are the dominant land covers in the Tajan River watershed and this landscape status has a direct connection with nitrate pollution. Understanding the correlations between landscape variables and nitrate pollutant is a priority in order to assess pollutants loading and predicting the impact on surface water quality. The soil and water assessment tool was used to simulate nitrate loads in different land cover types in different years. The landscape pattern was calculated by FRAGSTATS. The contributing share of each land use/land cover shows nitrate pollutant produced by grassland (5.7%) and forest (29%) are less than those produced by agricultural land (64.2%). Agricultural land was identified as the main source of nitrate pollution. Paddy fields and orchards had the most intensive soluble nitrate loss especially in spring and summer. Statistical analysis indicated that nitrate was positively associated with patch density, edge density, patch number, total edge, effective mesh size, largest patch index, and landscape shape index (p ≤ 0.01). We then analyzed how nitrate was related to landscape attributes in six different sites. Also the regression analysis results suggested that landscape metrics could account for more than 94% of the variance of nitrate in the whole catchment. The regression models confirmed the great importance of the agriculture metrics and forest metric in predicting nitrate in watershed. Defining the generation and extent of pollution in this particular watershed which discharges into the Caspian Sea can constitute an important step toward protecting this ecosystem. 相似文献
11.
Inhong Song Ik-Jae Kim Dae Ho Han Myeong-Seop Byeon Jae-Kwan Lee Moon-Seong Kang 《Paddy and Water Environment》2012,10(1):49-58
A majority of streams in Korea have been channelized and their adjacent flood plains have been converted for anthropogenic
land use, especially in urbanized areas. Fortunately, recent elevated public recognition to the stream ecosystem has led to
governmental efforts to conserve riparian areas. In this study, a simple method to prioritize locations for riparian establishment
was developed at a watershed scale based on spatiotemporal change of riparian forest area. The developed method was applied
for the Ansung and Sapkyo watersheds, which were under consideration for the stream riparian area establishment by the Korean
Ministry of Environment. Two riparian forest indices, Riparian Forest Index (RFI) and Riparian Forest Change Index (RFCI)
were developed to represent spatial and temporal change of watershed riparian forest, respectively. LANSAT satellite images
with a 30 m × 30 m resolution were used to estimate the two riparian forest indices. A precautionary approach, which intends
to preserve the existing riparian forests as much as possible, was applied by ranking sub-watersheds based on the two riparian
forest indices to prioritize locations for the riparian establishment at a sub-watershed level. The results showed that overall
urban land cover in riparian areas increased while forests and cropland decreased over the past 25 years. More importantly,
riparian forest removal occurred more rapidly in the riparian area, which is one of the most important niches for riparian
ecosystems, as compared to the entire watershed. Most riparian forests appeared to be located upstream of the watersheds,
and thus it is important to develop management measures to preserve existing riparian forests from human activities. The developed
approach could be a useful tool that can assist policy makers to prioritize locations for the riparian area establishment.
However, this method has limitations of only considering riparian forest area and therefore, other aspects such as stream
morphology as well as ecology needs to be incorporated into riparian area determination process as they become available in
the future. In addition, considering that substantial portions of riparian areas have already been disturbed, the restoration
aspect of the impaired riparian also needs to be investigated further. 相似文献
12.
海岸带地区因其特殊的海陆生态系统环境而成为土地利用/覆被变化(LUCC)研究的热点区域.本文以位于海峡西岸经济区东北翼的闽东海岸带作为研究对象,利用2000、2009和2014年3期Landsat TM/OLI影像作为数据源,对该区2000~2014年的土地利用动态变化特征进行分析.结果表明:研究区土地利用类型以林草地和耕地为主,其中林草地面积迅速扩增,研究期间共增加了1 047.24 km2,相比之下,耕地面积显著减少,近14a间共减少了959.45 km2;在人类活动影响下,水产养殖的动态变化最为剧烈,稳定性最差,而由于政府加强对建筑用地的集约利用,使其成为近14 a研究区最为稳定的土地利用类型,面积基本保持不变;闽东海岸带土地利用的集约化程度远超全国平均水平,土地利用程度综合指数达255.19,但2000~2009年间,研究区土地利用仍处于调整期,2009~2014年,随着经济的快速发展及前期的调整,土地利用效率有所提高,其变化量和变化率分别为4.86和0.019,土地利用步入发展期.本研究对闽东及其他地区的土地集约化利用及生态环境可持续具有指导意义. 相似文献
13.
The effect of land use change on drying streams was evaluated using a grid-based continuous hydrological model (PGA-CC). For a drying stream-progressed watershed (398.8 km2), the model was calibrated and validated using 7 years (2005–2011) of streamflow data at the watershed outlet with an average Nash–Sutcliffe model efficiency of 0.71. Based on the model simulation results for 36 years (1976 to 2011), both land use change and climate change decreased the 10-day minimum flow by 0.16 m3/s and increased the day counts below the annual average by 40.6 days/year. These changes resulted from the 8.7 % increase in urban area, 1.43-fold increase in groundwater use, and 1.1 °C temperature increase during the 36-year period. From the distributed results of the model, we identified the drying stream location and progression. The spring and winter seasons were relatively strongly affected, and drying streams were identified in more urbanized areas with greater groundwater use. 相似文献
14.
Tasuku Kato 《Paddy and Water Environment》2005,3(1):21-27
Water quality in the watershed mainly used for agriculture is degraded by nutrients from fertilizers and animal wastes. These diffuse (non-point) sources have accumulated in soils and been released into the river system for the long-term. In this paper, a water quality tank model classified by land use is modified for the accumulation, and total nitrogen (T-N) is simulated over 40 years in the Yamada River basin within the Lake Kasumigaura watershed, Japan. For considering the nitrogen balance, the model has a database comprising statistical data such as population, land use, rain, fertilizer, and animal waste; it calculates cumulative load in soils and dissolved load separately. The model simulated the measured data with relative error of 15% for runoff and 7% for T-N. Five scenarios for the reduction of cumulative load were developed as a countermeasure plan: soil washing, slow-release fertilizer, fertilizer application reduction, cover crop, and animal waste reduction. The results show that T-N first decreases and then increases after 30 years in the case of the slow-release fertilizer scenario and that T-N is reduced by 30% after 40 years in the case of the 100% animal waste reduction scenario. 相似文献
15.
Yasuhiro Tsujimoto Tovohery Rakotoson Atsuko Tanaka Kazuki Saito 《Plant Production Science》2013,16(4):413-427
ABSTRACTIn sub-Saharan Africa (SSA), rice production from smallholder farms is challenged because of a lack of fertilizer inputs and nutrient-poor soils. Therefore, improving nutrient efficiency is particularly important for increasing both fertilizer use and rice yield. This review discusses how to improve the return from fertilizer input in terms of agronomic N use efficiency (AEN), that is, the increase in grain yield per kg of applied N, for rice production in SSA. The AEN values we summarized here revealed large spatial variations even within small areas and a certain gap between researcher-led trials and smallholder-managed farms. Experimental results suggest AEN can be improved by addressing spatial variations in soil-related factors such as P, S, Zn, and Si deficiencies and Fe toxicity in both irrigated and rainfed production systems. In rainfed production systems, differences in small-scale topography are also important which affects AEN through dynamic changes in hydrology and variations in the contents of soil organic carbon and clay. Although empirical evidence is further needed regarding the relationship between soil properties and responses to fertilizer inputs, recent agricultural advances have generated opportunities for integrating these micro-topographical and soil-related variables into field-specific fertilizer management. These opportunities include UAV (unmanned aerial vehicle) technology to capture microtopography at low cost, database on soil nutrient characteristics at high resolution and more numbers of fertilizer blending facilities across SSA, and interactive decision support tools by use of smartphones on site. Small-dose nursery fertilization can be also alternative approach for improving AEN in adverse field conditions in SSA.ABBREVIATIONS: AEN: agronomic nitrogen use efficiency; FISP: farm input subsidy program; VCR: value cost ratio; SOC: soil organic carbon; SSA: sub-Saharan Africa; UAV: unmanned aerial vehicle 相似文献
16.
Prediction of paddy field change based on climate change scenarios using the CLUE model 总被引:1,自引:1,他引:0
Yun-Gyeong Oh Seung-Hwan Yoo Sang-Hyun Lee Jin-Yong Choi 《Paddy and Water Environment》2011,9(3):309-323
This study simulated land-cover change using the Conversion of Land Use and its Effects (CLUE) model and predicted future
changes in paddy field area under climate change scenarios A1B, A2, B1, and B2 of the Special Report on Emissions Scenarios
(SRES). The CLUE model is a dynamic spatial land-use simulation model considering competition among land-use types in relation
to socioeconomic and biophysical driving factors. Yongin, Icheon, and Anseong, South Korea, were selected as study areas,
and scenarios were developed for regional-level simulation of land-use change. Binary logistic regressions were also conducted
to evaluate the relationships between land uses and its driving factors. Finally, the simulation results suggested future
changes of paddy field area under the scenario conditions. In all the scenarios, demand for cropland, including paddy and
upland, decreased continuously throughout the simulation period of 2000–2100. The decrease in cropland area was particularly
steep in scenario A2 in 2050. The receiver operating characteristic (ROC) values indicated that the spatial patterns of land-cover
types based on the regressions were reasonably explained by the driving factors. According to the scenarios developed and
location characteristics, in scenario A1B, paddy field areas were mainly transformed into built-up areas, while in the other
scenarios paddy field areas were mainly transformed into forest. The approach used in this study is expected to enable exploration
of future land-use changes under other development constraints and detailed scenarios. 相似文献
17.
为了探讨灌水和非灌水条件下冬小麦对水分的利用特点,在大田条件下研究了灌水与非灌水两种处理对冬小麦的耗水结构、土壤水分利用程度及水分与产量之间的关系。结果表明,在非灌溉条件下,冬小麦主要利用20~60 cm土层中的水分,冬小麦对土壤贮水的消耗量增加,平均多耗水96.84 mm;土壤水分利用程度提高,较灌水区提高26.8个百分点;耗水系数增加,水分利用效率增大;冬小麦的产量与0~100 cm土层的含水量有密切的关系,这些土层内的含水量变动对产量的影响最大。 相似文献
18.
In-Kyun Jung Jong-Yoon Park Geun-Ae Park Mi-Seon Lee Seong-Joon Kim 《Paddy and Water Environment》2011,9(3):275-290
A grid-based, KIneMatic wave STOrm Runoff Model (KIMSTORM) is described. The model adopts the single flow-path algorithm and
routes the water balance during the storm period. Manning’s roughness coefficient adjustment function of the paddy cell was
applied to simulate the flood mitigation effect of the paddy fields for the grid-based, distributed rainfall-runoff modeling.
The model was tested in 2296 km2 dam watershed in South Korea using six typhoon storm events occurring between 2000 and 2007 with 500 m spatial resolution,
and the results were tested through the automatic model evaluation functions in the model. The average values of the Nash–Sutcliffe
model efficiency (ME), the volume conservation index (VCI), the relative error of peak runoff rate (EQp), and the absolute error of peak runoff (ETp) were 0.974, 1.016, 0.019, and 0.45 h for calibrated storm events and 0.975, 0.951, 0.029, and 0.50 h for verified storm
events, respectively. In the simulation of the flood mitigation effect of the paddy fields, the average values of the percentage
changes for peak runoff, total runoff volume, and time to peak runoff were only −1.95, −0.93, and 0.19%, respectively. 相似文献
19.
Human-wildlife conflict (HWC) is a growing global issue that seriously threatens agricultural production and livelihoods. Studying the relationship between wildlife damage, land use, and livelihood enables us to understand the dilemma facing current wildlife protection and ecological restoration policies and to amend existing policies effectively. Using participatory rural appraisal (PRA), quantitative analysis, and a Multilevel Logit regression model, this paper analyzed land use and livelihoods among 160 households subject to wild boar (Sus scrofa) damage in four villages within Youyang County in the poor mountainous areas of Chongqing, China. The findings showed the following: (i) wild boars in Youyang County were responsible for large-scale crop and property damage; (ii) cultivated land abandonment has become a significant trend in land use, and the most important perceived driver for abandoning farmland is the land plot's vulnerability to wild boar damage; (iii) when protecting cultivated land plots, households tend to protect those plots that are close to the road, have larger land area, and have a slight or abrupt slope; however, households with more members working in non-farm labor, more female agricultural workers, and/or higher non-farm income are more inclined to abandon protection of their plots. This paper discusses seven main measures that are frequently adopted by farmers to protect their crops and livestock and are perceived by these farmers as the most effective and sensible countermeasures. 相似文献
20.
Simulation of water quality with the application of system dynamics model for population and land-use changes 总被引:1,自引:0,他引:1
Tasuku Kato 《Paddy and Water Environment》2005,3(2):103-109
Water quality is degraded due to urbanization because it causes population growth and land-use changes in a watershed. These
changes are usually simulated using a linear equation; however, in reality, population and land use are very closely related.
A watershed system dynamics model (WSD model) was developed in the simulation of the relation among population, land use (paddy
fields, upland fields, forest, and household), and runoff. The model comprised of three sectors: the agricultural sector,
nature sector, and urban sector. The elements in the WSD model were selected based on interviews with local government officers
and references. The WSD model simulated population, land use, and runoff with an average relative error of about 5%. Total
nitrogen (T-N) and total phosphorus (T-P) were simulated using the results of the WSD model and unit effluent loads. Field
surveys were conducted to determine the rate of mitigation in paddy fields. In addition, correction equations for runoff and
phosphate-containing detergent were introduced. The model simulated T-N with an average relative error of 9%, and T-P with
27%; a sensitivity analysis for the principal elements in the WSD model showed reasonable results. 相似文献