Monitoring grey water footprint and associated environmental controls in agricultural watershed.

The grey water footprint (GWF) is an advanced index linking pollution load and water resources. However, the existing agriculture-related GWF was developed based on hydrological processes, which limits its role in watershed water pollution level (WPL) measurements. The main scope of this study is to calculate GWF and WPL based on runoff, total nitrogen (TN), and total phosphorus (TP) observations in the Hujiashan Watershed of China's Yangtze River Basin. Partial least squares structural equation modeling (PLS-SEM) was utilized to explore the impact pathways of environmental features on GWF and WPL. On this basis, propose measures for the management of this agricultural watershed. The results showed that the TN concentration had a V-shaped trend in 2008-2015, while the TP gradually decreased. The GWF calculations for the TN and TP were compatible with the temporal trends for the concentrations, which were higher in the wet season (0.45 m3/m2 for TN, 0.10 m3/m2 for TP) than in the dry season (0.11 m3/m2 for TN, 0.02 m3/m2 for TP) and increased from upstream to downstream. The WPLs of TN exceeded 2.0 in the midstream and downstream areas, whereas those for TP were inconspicuous. According to PLS-SEM, the GWF is primarily influenced by topographical variables and hydrological features, whereas the WPL is mainly controlled by hydrological features and landscape composition. Fertilizer reduction and efficiency measures should be implemented on farmland and appropriately reducing farming activities on slopes to relieve the GWF and WPL in the watershed.

Crop water footprints and their driving mechanisms show regional differences.

Identifying crop water footprints and their driving mechanisms is of significant importance for regional water resources management and ecological sustainability. However, there is currently a lack of comparative studies on drivers of crop water footprint among multiple regional types. In this study, based on quantifying the crop water footprints in seven regions (North China, Northeast China, East China, Central China, South China, Southwest China, and Northwest China) in mainland China from 1996 to 2020, the path analysis method was used to reveal their driving mechanisms. The results showed that the average annual agricultural water footprint was 1448.2 Gm3, with blue water, green water, and grey water accounting for 10.1 %, 66.6 %, and 23.3 %, respectively. Fruits and cereals jointly contributed 80 % of the total water footprint. The crop water footprint in East China was significantly higher than in other regions, accounting for 29.3 % of the national water footprint. The average crop production water footprint was 1080.4 mm, with the highest values observed in East China and South China, and the lowest in Northeast China and Southwest China. Except for East China, the crop production water footprint in other regions showed an increasing trend over time. Irrigation area ratio had the greatest impact on crop production water footprint except for Northeast China, while chemical fertilizer consumption significantly influenced crop production water footprints in North, East, Central, Southwest and Northwest China. Additionally, per capita GDP, per capita net income and irrigation water use efficiency also had considerable effects on crop production water footprint in Northwest China. The research findings can provide a valuable reference for the development of strategies for the efficient and sustainable utilization of agricultural water resources in different regions.

Ecological impact assessment of green virtual water flow in inter-provincial crop commutation within China.

Green water is crucial for to regional ecological sustainability. Currently, there is a lack of research on the impact of crop green water communication on the regional ecology in China. The ecological impact index (EII) and integrated ecological water supply (IES) were proposed to comprehensively evaluate the regional ecological impact of the green virtual water flow (GVWF) of crops. Based on the principle of trade cost minimization, this study simulated the inter-provincial crop commutation within China during 2010-2019 by assigning weights to production, demand, and transportation costs, and analyzed the impact of crop communication on regional ecology. The results showed that multi-year average GVWF among provinces was 216.45 Gm3, accounting for 33.7 % of the total green water footprint of crops. The ecological impact of GVWF varies among provinces and years. The EII values in Beijing, Shanghai, and Jiangsu were all >100, whereas it was <1 in Yunnan and Xizang. Regional management policies for water resources, ecology, and economic development should be formulated taking into account the IES and EII jointly. It is recommended to increase the export of green virtual water of crops and expand the ecological area while ensuring the utilization rate of green water in regions with higher EII values, such as Guangxi and Yunnan. In the future, it is important for district managers to prioritize the quality of ecological development and protect ecological areas from erosion while pursuing urban development. This study innovatively evaluated the ecological impact of crop communication in different regions, which has guiding significance for the trade management in the ecologically water-deficient areas.

Water resource use and driving forces analysis for crop production in China coupling irrigation and water footprint paradigms.

The crop water relationship quantification is conducive to decision-making for regional food safety and resource conservation. However, irrigation water and crop water footprint (CWF) was observed separately in previous studies, which leads to incomplete evaluation of water resource occupation in agricultural system. The crop water resource use (WRU), combining WF and irrigation water accounting, in 31 provinces of China from 1999 to 2018 was estimated in current paper. The driving forces of WRU were analyzed using the logarithmic mean divisia index (LMDI) model, based on its spatial and temporal patterns demonstration. The results showed that national WRU increased from 1051.6 Gm3 in 1999 to 1676.4 Gm3 in 2018, with an average annual growth rate of 2.48%. The provinces with high WRU were mainly distributed in North China and Northeast China. Hebei, Shandong, and Henan jointly contributed 28.9% of the national WRU. In addition, economic level was the largest contributor to promote the growth of WRU, and water use intensity was the most important contributor to inhibit the growth of WRU. Economic level, resource endowment, and population size had a promoting effect on WRU in Northeast, Northwest, North China, and Southeast provinces, while water use intensity, irrigation technique, and urbanization degree showed inhibitory effect in Northeast, Northwest, and Southwest provinces. It is meaningful to combine water footprint and irrigation water use for agricultural water management and conservation. The arid North China Plain should adopt water-saving irrigation and rainwater recycling technologies to control WRU, and the Northeast granary should reduce WRU by strengthening water pollution prevention and improving water resources scheduling to ensure food security and sustainable use of water resources.

Blue, green, and grey water footprints assessment for paddy irrigation-drainage system.

Water footprint (WF) quantifies the impact of paddy field evapotranspiration (ET) and non-point source pollution on water resources and is an evaluation index for water sustainability. However, it is difficult to measure accurately using the existing method, which is based on parameter assumption without considering the field water conditions. In this study, a generic and physically based method for blue, green, and grey water accounting in paddy rice cultivation is introduced. We conducted field experiments using the common flood irrigation (CFI) and water-saving irrigation (SWI) modes in Nanjing, East China. By tracing the sources of ET and the migration process of multiple pollutants (TN, TP, NH4+-N, and NO3--N), the characteristics of blue-green water consumption and the actual amount of water required to dilute pollutants at different growth stages of rice under CFI and SWI were analyzed. The WF of paddy rice was 1000 m3/t (49% WFgreen, 17% WFblue, 34% WFgrey) and 910 m3/t (50% WFgreen, 10% WFblue, 40% WFgrey) for CFI and SWI, respectively. The WF for paddy rice production was reduced by approximately 9% under SWI compared to CFI, with declines of 47% for WFblue and 8% for WFgreen. The SWI mode changed the ratio of blue to green water fluxes in field water by reducing irrigation during non-critical periods, and green water was used preferentially to enhance its utility. This conceptual method is the first to describe the formation mechanism of blue, green, and grey WFs in paddy systems. It can be extended to different scales and agro-ecosystems that show the influence of crop cultivation on water resources.

Assessment of the regional agricultural water-land Nexus in China: A green-blue water perspective.

An appropriate agricultural water-land nexus can help to effectively take advantage of limited water and land resources, which is of great significance for guaranteeing food security. An R index was proposed to evaluate the regional agricultural water-land nexus from a green-blue water perspective in the current paper. The effects of irrigation on the agricultural water-land nexus were revealed for the first time based on this index in evaluations of all (Rt) and irrigated (Ri) arable land in the 31 provinces, autonomous regions and municipalities (PAMs) of China during 1999-2018. The national annual average values of Rt and Ri were 1.94 and 3.55 m3/m2, respectively; the former was steady during the observed period, while the latter showed a significant decreasing trend (P < 0.01) from 4.35 m3/m2 in 1999 to 2.66 m3/m2 in 2018. The values of both Rt and Ri values in South China were higher than those in North China. The maximum values of Rt and Ri appeared in Xizang (Rt = 99.15 m3/m2; Ri = 201.99 m3/m2), while the minimum values occurred in Ningxia (Rt = 0.30 m3/m2; Ri = 0.44 m3/m2). The Gini coefficient for Ri (Gi) in each year was higher than that for Rt (Gt), demonstrating that the agricultural water-land nexus in irrigated arable land was highly imbalanced during the last two decades. From the perspective of the equitable distribution of irrigation water, irrigation facilities should be developed in the Southeast and Southwest PAMs to improve the effective irrigation rate. In addition, the government should simultaneously implement water transfer plans to reduce the agricultural water pressure in the PAMs in the North China Plain and Northeast China.

Unravelling resources use efficiency and its drivers for water transfer and grain production processes in pumping irrigation system.

Improving the resource utilization efficiency in irrigation systems contributes to the sustainability of the regional water-energy-grain nexus. Based on the water, energy and grain relationships quantification, the comprehensive efficiency (CE) of water transfer and grain production processes and its driving mechanism were analyzed, considering a pumping irrigation system in the Lianshui irrigation district (LID) in eastern China, as a case study. The annual crop output, crop water footprint, and electric energy consumption were estimated as 905.3 M kg (1 M = 106), 914.7 M m3 (50.7% blue water), and 3004.0 kWh, respectively, from 2005 to 2018; the corresponding crop water productivity (CWP), electricity energy productivity (EEP), water intake efficiency of electric energy (WIE) were 0.91 kg/m3, 80.39 kg/kJ, and 75.22 m3/kJ, respectively. CWP, EEP, and WIE varied among crops; however, none of the three indicators showed an obvious trend of change with time. The CE of integrated grain was 0.48 and showed an increase over time, indicating that the sustainability of the studied pumping irrigation system was improving. The driving effect of artificial factors (e. g. social development, agricultural input, and water management) on the CE was more obvious than that of natural conditions (e. g. climate). Increasing agricultural machinery and urbanization rates and reducing the agricultural water rate are conducive to improving the resource utilization efficiency in pumping irrigation systems. The analysis framework coupling water footprint and traditional paradigms proposed in this paper provides a feasible approach for the stability and sustainability of irrigated agricultural systems observation.

Development of global soil erosion research at the watershed scale: a bibliometric analysis of the past decade.

At the watershed scale, soil erosion is a cascading system that includes detachment-transport-deposition processes while sediment yield is the net balance of detachment and deposition at the watershed outlet. Due to the temporal-spatial variations of rainfall and landscapes, the relationships between soil erosion and sediment yield are complex and non-linear. Soil erosion processes and sediment yield at the watershed scale have attracted widespread attention; however, few systematic studies have been performed. In this study, a bibliometric analysis and visualization are used to understand the global research status of soil erosion and sediment yield at the watershed scale and provide a reference for researchers to establish future research directions. The USA and China were the most active contributors and had the most publications and active institutions, while Jean Poesen, D.E. Walling, and Xingmin Mu were the top three lead authors in this field. A keyword evolution analysis showed that determining the relationship between soil erosion and the watershed landscape and identifying the sediment source and off-site environmental and ecological effects caused by soil erosion have attracted considerable research attention. Additionally, significant progress has been made in the study of "connectivity," and future research should integrate connectivity and soil erosion models to explain the soil erosion, sediment transport, and deposition processes at the watershed scale.

Formation mechanism and step effect analysis of the crop gray water footprint in rice production.

Gray water footprint (GWF) is a simple and efficient indicator to quantify water pollution that has received extensive attention. Previously, an agricultural GWF was estimated by assuming the nitrogen loss rate throughout the crop cycle, while the field chemicals accompanying water movement during crop growth were not considered. In this study, using field observations of water and nitrogen transport in Nanjing, China, the GWF was calculated at the time steps of a day (GWFd), sub-growth period (GWFs), and whole crop season (GWFw), and its formation mechanism and step effect in rice production were explored. Field drainage and leakage caused nitrogen loss and generated a GWF, with the latter occurring intermittently. The values of GWFd, GWFs, and GWFw from 2015 to 2018 were 0.42, 0.38, and 0.31 m3/kg, respectively, and the step effect exists temporally for the rice GWF. The GWF of paddy rice growth decreased as the measurement period increased and the time step was calculated using GWFd as a reference. Herein, it was determined that the GWFw used in previous studies may have greatly underestimated the adverse impact of the GWF on water quality, particularly in humid regions or years. Therefore, it is essential to identify the formation mechanism and appropriately select the time steps for GWF evaluation during rice production. This research provides methodological references for GWF assessment and reduction in crop production systems.

Towards quantification of the national water footprint in rice production of China: A first assessment from the perspectives of single-double rice.

Rice is one of the most important crops in China, contributing to approximately 28% of total cereal yield. Despite substantial production, given that rice is a high water-consuming crop, the water shortage due to the irreversible decline in available water resources on a global scale induced by undergoing climate change will pose grave challenges to rice reproductive growth and related water resources utilization. As a consequence, investigating the responses of rice productivity and water consumption to more pronounced climate changes is of great significance for water resources sustainable utilization in terms of reducing irrigation water requirements and ensuring food security. Present water footprint (WF) methods do not calculate the weighted average of each WF component at the national level when evaluating the effects of prospective climate change upon rice production. The national water footprint (NWF), i.e. taking the share of each province in the total production of crops as weighting factors, has been regarded as an effective approach to determine where each WF component is originally located. In this study, the temporal change characteristics of NWF for single-rice (SR), early-rice (ER) and late-rice (LR) in different agro-ecological zones across China during 2001-2010 were assessed for the first time. The results exhibited that NWF of rice was an estimated 304,848 million cubic meters (MCM) per year. The SR accounted for the greatest portion of NWF, followed by ER and LR. The NWF rank was SR-V > SR-I > ER-VI > SR-IV > LR-III > LR-VI > SR-II > ER-III. The blue water footprint (WFb) presents decreasing trends in most agro-ecological zones (SR-I, SR-II, SR-IV, ER-III and LR-VI), while green water footprint (WFg) exhibits increasing trends within these regions. This study provides a beneficial approach for decision-making processes aiming at better agricultural water resources management strategies to alleviate water resources scarcity and reduce food risk in the context of surging demand, which will support agricultural water resources management of China towards a more balanced direction at the national level.

Variation and driving mechanism analysis of water footprint efficiency in crop cultivation in China.

Water footprint regulation in agricultural production is of great significance to regional food, water and ecological sustainability. The spatial-temporal characteristics and driving mechanism of water footprint efficiency (WFE) in crop cultivation in China during 1996-2015 were analysed based on the quantification of the crop-water relationship. The results showed that China's total crop water footprint (TWF) was 1125.6 G m3, and the blue, green and grey components accounted for 24.4%, 57.4% and 18.2%, respectively. The national WFE was 0.681 and increased over time due to the improvement of agricultural technology. Spatial autocorrelation analysis showed that provinces with similar WFE values were clustered geographically and have gradually weakened since 2012. Provinces with a high WFE were concentrated in the southeast and northeast, and low-value provinces were distributed in the west of China. The main anthropogenic driving factors were the preliminary fertilizer application intensity (FAI) and population density (PD); however, these factors have been replaced by the irrigation efficiency (IE), agricultural water use ratio (AWR) and irrigation area proportion (IAP) in recent years. Specific regions should formulate water resource management policies according to their WFE performance, agricultural production scale and water resource endowment. The northeast should control crop cultivation and enhance the yield to solve water shortage problems, the central provinces should improve WFE, and the southern provinces should contribute to the promotion of national water use efficiency by expanding crop sowing and irrigation areas. This study provides a reference for water resource management in the context of social and environmental change.

Analysis of the characteristics and driving forces of water footprint productivity in paddy rice cultivation in China.

BACKGROUND: Water productivity improvement is fundamental to agricultural water use control, and the water footprint provides a new and comprehensive method for identifying the crop-water relationship. This study is intended to explore the spatiotemporal pattern and driving forces underlying the rice water footprint productivity (WFP) in China during the years 1996-2015 based on calculations of the provincial blue, green, gray, and white water footprints. RESULTS: The national water footprint in paddy rice cultivation was 240.97 Gm3 , and green water accounted for 43.9% of the total. The WFP was 0.795 kg m-3 and increased over time in all 30 provinces for which it was calculated. The growth rate in the northern provinces was greater than that in the southern part of the country. The WFP clustered geographically in all years observed. High-value provinces were concentrated to the south of the Yangtze River, whereas most of the provinces that showed a low WFP were distributed in the north China and northwest subregions. Precipitation and sunshine hours were the most obvious driving factors of rice WFP. The effects of agricultural input, e.g., agricultural machinery power, pesticides, and irrigation efficiency, on WFP also could not be ignored. CONCLUSION: The WFP is a comprehensive and useful index of the crop-water relationship and water-use efficiency. Improving agricultural input and irrigation technology are reliable approaches for WFP promotion. Areas in northeast China showed the most urgent need for improving the rice WFP, and the inclusion of the main grain producing areas in the Yangtze River Basin will further reduce ineffective water occupancy to improve water-use efficiency. © 2019 Society of Chemical Industry.

Assessment of climate change impact on the water footprint in rice production: Historical simulation and future projections at two representative rice cropping sites of China.

As one of the most important crops cultivated in China, rice contributes to approximately 28% of total yield. In despite of the substantial production, rice productivity is gravely affected by ongoing climate change and reduction of available water resources. Thus, assessing the responses of rice water consumption and productivity to more pronounced climate change is of great significance to water resources management in terms of relieving the resources shortage and meeting the food demand. In this study, the yield and water resources utilization during 1961-2010 in two typical rice plantation regions of China were evaluated using validated rice model ORYZA2000. Subsequently, their responses to future climate scenarios of 21 century were investigated through driving ORYZA2000 with downscaling climatic projections from GCMs under four RCPs emission scenarios. To quantify the water resources utilization in rice production from multiple perspectives, the water footprint (WF) and three water productivity indices (WPI, WPU and WPET) were integrated for assessing the regional agricultural water stress in this paper. The results revealed that the annual average linear inclining rates of WF in two stations (Kaifeng and Kunshan) were 3.86 m3/ t and 2.62 m3/ t, respectively. Moreover, compared with the green water footprint (WFg), the blue water footprint (WFb) is projected to significantly increase in future. The water productivity (WP) would decrease in two stations under four RCPs scenarios except that the WPu and WPET of Kunshan under RCP2.6 and RCP4.5 scenario in 2020s, 2050s and 2080s. Hence, this study provides insights into comprehensively understand the influences of climate change on food security and sheds lights on the regional strategy for future water resource management.

Water for maize for pigs for pork: An analysis of inter-provincial trade in China.

Trade in commodities implies trade in virtual water (VW), which refers to the water that was used to produce the traded goods. Various studies have quantified international or inter-provincial virtual water (VW) flows related to the trade in crops and animal products. Until date, however, no effort has been undertaken to understand how the water embodied in traded feed crops (trade stage TS1) will be transferred further because of trade in animal products (trade stage TS2). This is the first study showing this mechanism, in a case study in China for maize (the major pig feed) and pork (the dominant meat), considering the period 2000-2013. We estimate the annual green and blue water footprints in maize production and then quantify the inter-provincial VW flows related to trade in maize (TS1) and trade in maize embodied in pork (TS2). Results show that in TS1, maize-related VW flowed from the water-scarce North to the water-rich South, with an increase of 40% over the study period (from 43 to 61 billion m3 y-1). In TS2, about 10% of the water embodied in maize exports from North to South China returns in the form of pork, with an increase in the absolute amount of 25% (from 4.8 to 6.1 billion m3 y-1). Considering blue VW flows specifically, we find that North-to-South blue VW flows decreased by 5% in TS1, while South-to-North blue VW flows increased by 23% in TS2.

Feasibility study of a human papillomavirus E6 and E7 oncoprotein test for the diagnosis of cervical precancer and cancer.

Objective To evaluate the clinical value of human papillomavirus (HPV) E6 and E7 oncoprotein (HPV E6/E7) detection in the early screening of cervical cancer. Methods This prospective study evaluated all patients with suspected cervical intraepithelial neoplasia (CIN) as identified by the presence of at least one positive indicator from a ThinPrep cytologic test (TCT) and/or a Hybrid Capture 2 (HC2) HPV DNA test. The levels of E6/E7 oncoproteins were determined using Western blot analysis. The diagnostic value of the HPV E6/E7 protein assay was compared with the clinical diagnosis from TCT, HC2 and the gold standard of cervical biopsy histology. Results A total of 450 patients were enrolled in the study and based on histological findings, 102 patients were diagnosed with CIN1 (22.7%), 241 with CIN2 (53.6%), 96 with CIN3 (21.3%) and 11 with squamous cell carcinoma (2.4%). For a diagnosis of CIN2+, although the sensitivity of the HPV E6/E7 assay was lower than HC2 (65.5% versus 96.6%, respectively), the specificity was higher (38.2% versus 5.9%, respectively). The sensitivity of the HPV E6/E7 assay was higher than TCT (65.5% versus 36.2%, respectively). Conclusion Measuring HPV E6/E7 oncoprotein levels is a potential new biomarker for HPV type 16.

An evaluation of the water utilization and grain production of irrigated and rain-fed croplands in China.

Irrigation plays a major role in Chinese agricultural production, as China is experiencing water and food scarcity. Assessing water use (WU) and water productivity (WP) will contribute to regional water management and grain production improvement. This paper quantifies the water use and productivity in grain production for 31 Chinese provinces, autonomous regions and municipalities (PAMs) by distinguishing between irrigated and rain-fed farmland. An indicator of marginal productivity of blue water (MWPb) is established and calculated to evaluate irrigation profits. National water use (WUt) for grain cultivation from 1998 to 2010 was approximately 689.04 Gm(3) (42.26% blue water and 57.74% green water). The productive water proportions for irrigated and total croplands were 65.57% and 76.85%, respectively. Water use compositions from both blue-green and productive-unproductive perspectives changed slightly over time. The water use productivity (WPU) and water consumption productivity (WPC) for integrated grain products of China during the study period were 0.747 and 0.972 kg/m(3), respectively. The spatial distribution patterns of irrigated WPs (WPUI, WPCI) were consistent with those for total cropland. China has achieved sufficient food supply without increasing water use. The national MWPb was estimated to be 0.673 kg/m(3), revealing a higher increase in crop yield on irrigated land compared to rain-fed land. The northeast provinces urgently need to improve irrigation efficiency, and the North China Plain PAMs should promote rain-fed crop yield to increase grain production and control water use in the future.

Impacts of changing cropping pattern on virtual water flows related to crops transfer: a case study for the Hetao irrigation district, China.

BACKGROUND: Analysis of cropping patterns is a prerequisite for their optimisation, and evaluation of virtual water flows could shed new light on water resources management. This study is intended to explore the effects of cropping pattern changes between 1960 and 2008 on virtual water flows related to crops transfer in the Hetao irrigation district, China. RESULTS: (1) The sown area of crops increased at an average rate of 3.57 × 10(3) ha year(-1) while the proportion of sown grain crops decreased from 92.83% in the 1960s to 50.22% in the 2000s. (2) Virtual water content decreased during the study period while net virtual water exports increased since the 1980s. (3) Assuming that the cropping pattern was constant and was equal to the average 1960s value, accumulated net virtual water export in 1980-2008 would have been 4.76 × 10(9) m(3) greater than that in the actual cropping pattern scenario. CONCLUSION: Cropping pattern changes in the Hetao irrigation district could not only be seen as resulting from the pursuit for higher economic returns, but also as a feedback response to limited water resources. A systematic framework is still needed for future cropping pattern planning by taking food security, continued agricultural expansion and other constraints into consideration.

[Investigation on the impact of imported cases on filariasis elimination program in Shandong Province].

OBJECTIVE: To study the impact of imported filariasis cases on the elimination program in different areas of Shandong Province. METHODS: Dezhou was selected as former low endemic area and Yicheng as former high endemic area. Blood examination was carried out for both mobile population and local people for microfilariae(Mf). Mosquitoes were caught in field and dissected to count the ratio of those having laid eggs and the natural filarial infection rate. Mosquitoes reared at different temperatures were fed with Mf-positive blood and dissected after certain time period to observe the development of the larvae. The vectorial capacity and case transmission quantity were calculated and compared with those from different areas. RESULTS: The Mf positive rate of inflow population was 3.18% in average. No case was detected from 9,411 local residents after blood exam in Dezhou while 2 out of 692 local residents were found Mf positive in Yicheng. Mosquitoes natural infection rate was 3.81% but no third stage larva was found. The shortest time period needed for the larva to develop into an infective stage was 16 days in Dezhou and 11 days in Yicheng. The time period from blood meal to egg-laying on average was 4.95 days in Dezhou and 4.33 days in Yicheng. The ratio of vectorial capacity and case transmission quantity was 1:4.41 and 1:5.82 respectively in Dezhou and Yicheng. CONCLUSION: Filarial transmission seems unlikely in Dezhou for its low vectorial capacity and low transmission quantity resulted from low and evidently fluctuating temperature in the north. A low level filarial transmission may be possible in former high-endemic area such as Yicheng if there are as many imported cases as in Dezhou.