Development of a water quality tank model classified by land use for nitrogen load reduction scenarios

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.     

Classifying plant species indicators of eutrophication in Korean lakes

The objectives of this study were to establish a method of classifying plants as indicator species of eutrophication, as a key metric for assessing lake ecosystem health, and to select sensitive and tolerant plant species among aquatic macrophytes and hygrophytes. Thus, 38 natural and artificial lakes throughout Korea were investigated. The distribution and abundance of plant species were investigated. As a measure of eutrophication, the modified trophic state index (TSI_KO), derived from total phosphorus and chlorophyll a, was used. Using TSI_KO criteria and the response curves of plants to TSI_KO, a selection method of classifying sensitive and tolerant species was developed. Overall, 15 sensitive and 11 tolerant species among 117 macrophytes and hygrophytes were classified. The applicability of the selected indicator species was verified by a comparison with the results of a multimetric analysis using eight variables. The results suggest that the selected indicator species is expected to be useful as a metric for assessing lake ecosystem health.     

An evaluation of water-yield relations in maize (Zea mays L.) in Turkey

The objective of this study was to compare the responses of maize (Zea mays L.) to deficit irrigation. A field experiment was conducted during the 1999 and 2000 growing seasons in western Turkey. Irrigation treatments were tested with 100, 70, 50, 30 and 0% replenishment of water depleted at 120 cm soil profile from 100% replenishment treatment at ten days intervals. The irrigation amount ranged between 0 and 323.20 mm in the first year and 0-466.61 mm in the second year of the experiment. Seasonal crop water use values were between 142.19 and 481.91 mm in 1999 and 136.25-599.45 mm in 2000. Average maximum and minimum yields were 10639-10383 kg ha(-1) for full irrigated treatment (I100) and 3750-2136 kg ha(-1) for non-irrigated treatment (I0) in 1999 and 2000, respectively. Water deficit significantly affected maize yield. In both years, yield increased linearly with irrigation applied but the relationship varied from one year to the other. Water Use Efficiency (WUE) ranged from 1.49 to 2.71 kg m(-3), while Irrigation Water Use Efficiency (IWUE) varied from 1.44 to 2.55 kg m(-3) in both years. The yield response factor (ky) relating relative yield decrease to relative evapotranspiration deficit was found to be 0.99 for the data of the two experiments combined. Also, dry matter yields (DM) and leaf area index (LAI) were markedly affected by the irrigation treatments. The finding of this work showed that well-irrigated treatment should be used for maize grown in semi arid regions under no water scarcity.     

Mixing by wind-induced flow and thermal convection in a small, shallow and stratified lake

Thermal stratification is one of the important features in closed water bodies, which primarily depend on meteorological conditions, and has strong impact on the ecological environment in lakes or reservoirs. Data monitored in 3 days were analyzed for factors that affect heat mixing processes to examine the diurnal stratification cycles in the Shikinawa Lake, a study area in Fukuoka prefecture, Japan. We found that wind speeds and directions played an important role in the thermal mixing in the lake. High solar heating mainly caused stratification state, but with less effect under stronger wind action. Development of mixed layer depth in a natural lake due to wind-induced flow and thermal convection were calculated. Functional relationships between entrainment rate and Richardson number or Wedderburn number were found and represented in this paper. Besides, heats exchanged at the air–water interface and energy stored in the water column were also analyzed and discussed.     

Relation of Root Growth of Rice Seedling with Nutrition and Water Use Efficiency Under Different Water Supply Conditions

The arid/semiarid regions contribute the forty- three percent of crop planted each year. In these regions, rice is mostly grown under rainfed conditions, where the chances plants to face drought are during the growing season. The primary determinant of cr…     

Water quality monitoring and multivariate statistical analysis for rural streams in South Korea

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.     

洞庭湖区滩地及稻田洼地资源分布研究

洞庭湖是我国第二大淡水湖,也是承接湘、资、沅、澧四水和吞吐长江洪道调蓄型湖泊。随着三峡的建成,以及全球气候的变化,湖区受到洪水及干旱季节交替变化,呈现涨水为湖,落水为洲的变化规律,稻田洼地及滩地的面积伴随着改变。但是对于其时空分布规律、与水位变化的关系及资源总量没有确切的数据。而系统地掌握其演替规律,对洞庭湖生态经济区的建设与发展意义重大。因此,本研究利用1996—2016年的18期Landsat TM遥感影像数据,提取三峡建成前后,洞庭湖区滩地及稻田洼地面积,结合城陵矶水文及气象数据,分析洞庭湖区水面、水陆交错带滩地及稻田洼地资源的时空演变规律。结果显示：湖区滩地平均面积为21.93×10⁴ hm²,空间上呈聚集型分布与湖堤内、湖岸带及三口四水的河堤内,三峡蓄水前（23.27×10⁴ hm²）较蓄水后（21.26×10⁴ hm²）减幅达8.62%,面积东洞庭（12.43× 10⁴ hm²）>南洞庭（5.71×10⁴ hm²）>西洞庭（3.80×10⁴ hm²）,与行政区划面积正相关,年际变化与湖区水位变化呈负相关的变化规律;稻田洼地平均面积为4.75×10⁴ hm²,空间上呈随机且较均匀斑块分布于湖区围湖造田后形成的堤垸及三口四水冲积而成的湖盆地内,远离湖心的区域,蓄水前（5.14×10⁴ hm²）较蓄水后（4.56×10⁴ hm²）减幅达11.34%,面积岳阳市（2.29×10⁴ hm²）>常德市（1.61×10⁴ hm²）>益阳市（0.85×10⁴ hm²）。各县级行政区划的滩地及稻田洼地在三峡建成前后减幅明显;采用Pearson相关性分析及主成分分析可知,影响滩地及稻田洼地分布因子可分为2个主成分,第一主成分为“枯水期”性状,包括冬季月平均温度、冬季水位、冬季降雨量、稻田洼地面积及冬季流量等指标;第二主成分可称“丰水期”性状,包括夏季月平均温度、夏季流量、夏季水位、滩地面积、夏季降雨量等指标,构建的分析模型较可靠,能为湖区滩地及稻田洼地综合利用提供较好的理论基础。     

Trophic status and primary production in Lake Choghakhor, Chaharmahal-Bakhtiyari Province, Islamic Republic of Iran

In this study, trophic state indicators, total phosphate, algal chlorophyll and Secchi disk transparency and zooplankton community of Lake Choghakhor was studied monthly between May 2003 and April 2004. This lake is a shallow ecologically and economically important water body in eastern part of Iran. Crop farming and recreational activities are examples of the human impact around and within the lake, leading to a loading of DIN (Dissolved Inorganic Nitrogen) and TP (Total Phosphate) into the lake. Now submerged plants especially Myriophyllum spicatum has covered almost the entire lake and dense macrophyte beds (Polygonom amphibium), located on the East Southern end of the lake appear to act as a sink for these nutrients. Lake Choghakhor appeared to be in a macrophyte dominated clear water state with low TP (annual mean: 24 +/- 15 microg L(-1)) and chlorophyll a (annual mean: 3 +/- 1.28 microg L(-1)) concentrations and very high Secchi depth. The grazing pressure of dominant pelagic filtering zooplankton Daphnia longespina did not seem to be significant in determining the low phytoplankton crop expressed as chlorophyll a. We expect that sequestering of nutrients by submerged plants and associated epiphytes are the dominant stabilizing mechanisms suppressing the phytoplankton crop of Lake Choghakhor.     

The SRI (system of rice intensification) water management evaluation by SWAPP (SWAT–APEX Program) modeling in an agricultural watershed of South Korea

Paddy and Water Environment - In this study, a potential system for achieving rice intensification (SRI) water management in an agricultural watershed of South Korea was evaluated using the...     

Safe application of reclaimed water reuse for agriculture in Korea

This article describes the pilot study on the water reuse for agricultural irrigation in Korea. The project is a part of the application of wastewater reuse system for Agriculture project, a 21st Century Frontier R&D Program sponsored by the Ministry of Education, Science, and Technology and associated with the Sustainable Water Resources Research Program. The goal of the project was to develop infra-technologies necessary to reclaim wastewater for irrigation in agriculture. The project involved two phases: laboratory and field research. Reclamation techniques for irrigation and feasible reuse were developed as a first step in proposing appropriate water quality standards. Reclaimed wastewater of various qualities was used to irrigate cereal crops and vegetables, and possible adverse effects on crops, humans, and the environment were investigated. The optimal reclamation methods required to satisfy water quality standards were explored and the operational characteristics investigated. Moreover, an inventory of farmlands that could reuse reclaimed wastewater was established. Feasible delivery systems for irrigation were developed, and pilot project sites were identified. Finally, operational field data from pilot units were collected and analyzed. This research and development may help solve water shortage problems in Korea, which left unaddressed will have an adverse effect on future generations.     

小麦冠层不同光质透光率与叶面积指数的定量关系研究

为探究小麦叶面积指数(LAI)的空间分布及与不同光质透光率间的关系,通过三年田间试验,设置不同品种、氮肥水平和灌水次数,测定分析了小麦拔节期至灌浆后期冠层不同空间层次的透射光及叶面积指数(LAI),并对不同光质透光率与LAI间进行回归分析。结果表明,小麦LAI随生育时期的推进呈单峰动态变化,最高值出现在抽穗-开花期,且随灌水和施氮水平的增加而增大;光合有效辐射(PAR)透光率随生育时期呈先降后升趋势,且随灌水和施氮水平的增加而减小。LAI与PAR透光率均存在时空异质性,叶面积的垂直分布直接影响冠层内光分布。水氮处理对植株上层LAI影响较小,而对下层影响较大;40 cm处透光率递变明显,低水高氮以及高水低氮处理对透光率递减的影响较大。不同光质透光率均随冠层高度的下降均出现不同程度消减,透光率与向下累积LAI间均呈显著指数相关,相关性由强到弱依次为红边、蓝光、光合有效辐射(PAR)、绿光、近红外和红光。经回归分析,红边和蓝光透光率与LAI的定量关系表现较好,拟合性均优于PAR,尤其是红边透光率(R²=0.749),因此可以利用红边透光率建立模型,以监测小麦冠层LAI。     

Evaluation of N and P mass balance in paddy rice culture along Kahokugata Lake, Japan, to assess potential lake pollution

Kahokugata Lake, a closed lake, has been subject to eutrophication. This research was conducted to clarify the actual phenomena and evaluation of the discharges of N and P from paddy test fields in the lowlands into Kahokugata Lake. A comprehensive mass balance of N and P was obtained from 4 years of study. About N, the mean value of harvested unhulled rice (79.9 kg/ha) was greater than mean controlled release fertilizer inputs (56.7 kg/ha). Other inputs and outputs include N in atmospheric acid deposition (21.4 kg/ha) and N fixation–denitrification (9.2 kg/ha). The rice straw recycled after harvest was balanced by straw produced in the succeeding year. The runoff and percolation losses discharged into the lake was 11.3 kg/ha, (8.6% of total inputs). Since the rice harvested was consumed domestically, which taking out from the farmland and, therefore, nitrogen pollutant into the lake was becoming small, paddy rice at this site is considered an “anti-polluting, purifying or cleansing” crop. The P content in harvested rice (39.4 kg/ha) was balanced by fertilizer inputs (36.4 kg/ha). Previous studies examining inflow–outflow relationships without considering a comprehensive mass balance may lead to erroneous conclusions. Our findings indicate paddy rice in lowlands could be an environmentally friendly crop and can play an important role in reducing pollution of lakes, and therefore should be considered in land use planning.     

The geochemical characteristics of sediment in Tondano Lake,Indonesia: heavy metals and organic matter contents,and grain size distribution

Sediment quality of Tondano Lake, Indonesia has been investigated through measuring the geochemical characteristics such as the content of heavy metals, organic matter and grain size distribution; and also the relationship between heavy metals and organic matter, and between heavy metals and grain size distribution. These could be used as preliminary data for the purpose of evaluating lake condition as a part of freshwater ecosystem. The Tondano sediment had contained some heavy metals such as Cr, Cu, Hg, and Zn; where Cr and Zn, both less than the Sediment Quality Guideline (SQG), but Cu and Hg were well within the SQG. Organic matter content was highest at the northern outlet area, with the lowest amount at the southern inlet area. Grain size distribution was mostly dominated by sandy-loam clay (the highest content was at central lake). This was a result of intensive agricultural activities surrounding the lake, which brought sand grain via rivers from all areas to the central lake. The heavy metal contents were not found to be correlated with the organic matter, nor the grain size distribution (clay content).     

西瑁洲岛附近海域水质环境特征研究

根据2015年6月对西瑁洲岛海域环境监测的结果,用单项水质参数法、水体有机污染指数法和富营养化指数法对西瑁洲岛海域水质环境质量进行评价。评价结果表明：所监测站位中单项水质参数所变化范围为0.11～0.99,有机体评价因子均小于0,海域水质富营养化E测定值变化范围为0.006～0.027,说明西瑁洲岛海域水质良好。本次调查结果与2010年进行比较,无机氮、油类和锌的含量略有增加,但仍符合第一类海水水质标准,其他测项基本保持在同一水平。表明自2010年以来,西瑁洲岛海域的水质环境质量一直保持良好。     

Effect of arabinoxylans and laccase on batter rheology and quality of yeast-leavened gluten-free breads

The supplementation effects of maize fiber arabinoxylans (MFAX, 0%–6%), laccase (0–2 U/g flour) and water absorption level (90%–100%) on gluten-free (GF) batter rheology and bread quality were analyzed. From viscoamylograph analysis, lower starch amount in GF flour due to MFAX addition decreased peak viscosity and retrogradation. Surface response plots showed that laccase did not have significant effect on GF batter rheology and bread quality, whilst water was the most important variable. Higher levels of water absorption benefited bread texture. Higher water level (>100 mL/100 g flour) was needed in the experimental design to evaluate correctly the effect of 6% MFAX replacement on GF bread quality. Further analyses were carried in order to adjust water absorption of batters according to their consistency index (K ≈ 100 Pa sⁿ), resulting an optimal water absorptions of 95%, 100% and 105% for control flour and flours supplemented with 3% or 6% MFAX, respectively. Thus, MFAX addition enhanced water-binding capacity of flour and yielded GF breads with higher specific volume and softer crumb texture. These quality parameters were best rated with 6% MFAX addition to flours. This research demonstrated the potential of MFAX to develop GF breads with improved quality, when optimal water level is used.     

Estimation of flood risk index considering the regional flood characteristics: a case of South Korea

Global warming is increasing the variability of climate change and intensifying hydrologic cycle components including precipitation, infiltration, evapotranspiration, and runoff. These changes increase the chance of more severe and frequent natural conditions, and limit ecosystem function and human activities. Adaptation to climate change requires assessment of the potential disaster risk. The objectives of this study were to estimate the flood risk index (FRI) considering regional flood characteristics at the national level and to prioritize the factors affecting flood risk through principal component analysis. FRI was estimated based on the Delphi survey results from 50 water resources experts in South Korea. The potential risk analysis was conducted for 229 local governments in South Korea. The results showed that natural and social factors were more influential flood risk factors to South Korea than administrative and economic and facility factors. Specifically, natural, social, administrative and economic, and facility factors were, respectively, highest at Jindo-Gun in Jennam-Do, Gumi-Si in Kyongsanbuk-Do, Dong-Gu in Incheon-Si, and Suwon-Si, Kyonggi-Do. Overall, the highest FRI is shown in Anyang-Si, Kyongggi-Do. The spatial distribution of the FRI was high in the southeastern coastal region and basins of the two biggest rivers in South Korea, and normalized flood frequency followed spatial patterns similar to FRIs. This study provided information on the relative flood risk index among administrative units for investment prioritization in flood risk management. In this regard, the suggested FRI is expected to significantly contribute to methodical and economic improvements in budget allocations for flood risk management.     

Distribution of Water between Wheat Flour Components: A Dynamic Water Vapour Adsorption Study

The water adsorption properties of hard and soft wheat flours and flour components (starch, damaged starch, gluten, soluble pentosans, and insoluble pentosans) were determined at 25 °C using a controlled atmosphere microbalance. At different levels of relative humidity (from 10% to 95%), changes in sample mass (i.e., water gain) were continuously measured versus time and described using exponential models (R²≥0·994). Water adsorption isotherms were constructed for wheat flours and flour components and described using Guggenheim-Anderson-de Boer models (R²≥0·997). It was not possible to distinguish between the selected hard and soft wheat flours by their isotherms. The water-soluble pentosans had the highest water adsorption capacity. The theoretical distribution of water between the flour components (calculated using the Guggenheim-Anderson-de Boer parameters) was starch, 88%; gluten, 10%; and pentosans, 2%.     

Influence of weather factors on the incidence of Alternaria blight of cluster bean (Cyamopsis tetragonoloba (L.) Taub.) on varieties with different susceptibilities

Progression of Alternaria blight intensity was observed fortnightly during 1997 and 1998 on six varieties of cluster bean ranging in their susceptibilities to the disease. The disease progressed faster on the most susceptible variety (FS-277) during both the years. There was a significantly positive correlation between the disease severity and certain weather parameters (cumulative rainy days and cumulative rainfall) whilst maximum temperature was significantly negatively associated (pooled basis). The step-wise multiple regression analysis of data revealed that minimum temperature, relative humidity in the evening, sunshine and cumulative rainfall played a major role in disease development.     

Characterisation of spatial patterns of regional paddy rice with time series remotely sensed data

Remote sensing has facilitated the identification of acreage and spatial distribution of field crops with obvious seasonal dynamics. The primary objective of this study is to identify the spatial patterns of double-season early rice, single-season middle rice and double-season late rice of Hunan Province and Yuanjiang City, China, in 2010, using two kinds of time series remotely sensed imagery: 8-day composite MODIS surface reflectance product data (MOD09A1) and HJ-1A/B satellite images with a 4-day revisit period. The available MODIS and HJ-1 CCD images of transplanting and heading stages were first assured in accordance with the schedules of local traditional paddy fields tillage. Based on the MOD09A1 data product, time series normalised difference vegetation index (NDVI) images were calculated and smoothed to remove the noise and the atmospheric effects. Second, the spatial distribution and planting acreage of three types of rice of Hunan Province were derived from combining the enhanced vegetation index and land surface water index according to the water background and variation characteristics of NDVI values at transplanting and heading stages. Conversely, a two-test procedure was used to finish the identification of paddy rice in Yuanjiang City using time series HJ-CCD imagery. The first test was to derive the potential rice pixels using the NDVI image (?NDVI) between heading and transplanting stages, and the second test was to remove the non-rice pixels using maximum likelihood supervised classification. The experimental results showed that three types of rice were mainly distributed along the Dongting Lake Basin in Hunan Province and the relative errors were ?10.99, 1.46 and ?5.87 %, respectively, while they were primarily planted in the northern plains of Dongting Lake in Yuanjiang City, where the relative errors were 12.1, 16.7 and 0.8 %, respectively. We conclude that transplanting and heading stages are the best phenological combinations for identifying paddy rice through remote sensing time series analysis, and this study can provide a basis for evaluating paddy rice yield on a large scale .     

Recreational exposure to low concentrations of microcystins during an algal bloom in a small lake

We measured microcystins in blood from people at risk for swallowing water or inhaling spray while swimming, water skiing, jet skiing, or boating during an algal bloom. We monitored water samples from a small lake as a Microcystis aeruginosa bloom developed. We recruited 97 people planning recreational activities in that lake and seven others who volunteered to recreate in a nearby bloom-free lake. We conducted our field study within a week of finding a 10-μg/L microcystin concentration. We analyzed water, air, and human blood samples for water quality, potential human pathogens, algal taxonomy, and microcystin concentrations. We interviewed study participants for demographic and current health symptom information. Water samples were assayed for potential respiratory viruses (adenoviruses and enteroviruses), but none were detected. We did find low concentrations of Escherichia coli, indicating fecal contamination. We found low levels of microcystins (2 μg/L to 5 μg/L) in the water and (<0.1 ng/m³) in the aerosol samples. Blood levels of microcystins for all participants were below the limit of detection (0.147μg/L). Given this low exposure level, study participants reported no symptom increases following recreational exposure to microcystins. This is the first study to report that water-based recreational activities can expose people to very low concentrations of aerosol-borne microcystins; we recently conducted another field study to assess exposures to higher concentrations of these algal toxins.