Seasonal fluctuation of groundwater in an evergreen forest, central Cambodia: experiments and two-dimensional numerical analysis

This study of a water cycle was conducted in an evergreen forest located in the Mekong River Basin in central Cambodia. At the observation site, we measured the dynamics of the spatial distribution of groundwater levels. The groundwater movement was analyzed two-dimensionally using boundary conditions and parameters that had been observed in the field. The climate in the research area is dominated by two seasons, which occur annually: a rainy and a dry season. The groundwater levels are generally high during the rainy season and low during the dry season. Groundwater levels were measured along a stream, which flowed through the study site. The streambed was visible at the head of the stream in January. At the next downriver well point, the streambed appeared in March. Finally, it became visible at all well points in April, meaning that surface runoff had disappeared temporarily and instead flowed underground during the ensuing dry period. Groundwater levels of the studied lateral flow perpendicular to the stream that seeped and infiltrated into the stream were 1.2–2.5 m deep (in April), which was the lowest level recorded for the year. During that period, the depth of the groundwater of the studied lateral flow fell by as much as 56 mm per month. In addition, the lateral flow groundwater infiltrated into groundwater of the stream during that period. The groundwater level fluctuation was estimated based on a two-dimensional analysis of lateral flow perpendicular to the stream using a numerical simulation model with soil physical parameters and observed boundary conditions. The observations of ground water fluctuations were well reproduced. Deep seepage of groundwater was estimated using a uniform boundary condition that allowed efflux through the bottom, estimated as being approximately 30 mm per year. The simulated deep seepage rate was considered plausible considering other hydrological components such as soil water storage fluctuation.     

Future potential impacts of climate change on agricultural watershed hydrology and the adaptation strategy of paddy rice irrigation reservoir by release control

This study is to assess the climate change impact on the temporal variation of paddy rice irrigation reservoir water level from the future evaluated watershed inflow, and to suggest an adaptation method of the future reservoir water level management for stable water supply of paddy irrigation demands. A 366.5 km² watershed including two irrigation reservoirs located in the upper middle part of South Korea was adopted. For the future evaluation, the SLURP model was set up using 9 years daily reservoir water level and streamflow records at the watershed outlet. The average Nash-Sutcliffe model efficiencies for calibration and validation were 0.69 and 0.65, respectively. For the future climate condition, the NIES MIROC3.2 hires data by SRES A1B and B1 scenarios of the IPCC was adopted. The future data were downscaled by applying Change Factor statistical method through bias-correction using 30 years past weather data. The results of future impact showed that the future reservoir storages of autumn and winter season after completion of irrigation period decreased for 2080s A1B scenario. Considering the future decrease of summer and autumn reservoir inflows, the reservoir operation has to be more conservative for preparing the water supply of paddy irrigation, and there should be a more prudent decision making for the reservoir release by storm events. Therefore, as the future adaptation strategy, the control of reservoir release by decreasing in August and September could secure the reservoir water level in autumn and winter season by reaching the water level to almost 100% like the present reservoir water level management.     

Hydrologic impact of climate change with adaptation of vegetation community in a forest-dominant watershed

This study evaluated the impact on watershed hydrology by predicting future forest community change under a climate change scenario. The Soil and Water Assessment Tool (SWAT) was selected and applied to Chungju dam watershed (6,642 km²) of South Korea. The SWAT was calibrated and validated for 6 years (1998–2003) using the daily streamflow data from three locations. For the future evaluation of forest community and hydrology, the MIROC3.2 HiRes monthly climate data were adopted. The future data were corrected using 30 years (1977–2006, baseline period) of measured weather data, and they were daily downscaled by the Long Ashton Research Station-Weather Generator statistical method. To predict the future forest vegetation cover, the baseline forest community was modeled by a multinomial LOGIT model using variables of baseline precipitation, temperature, elevation, degree of base saturation, and soil organic matter, and the future forest community was predicted using the future precipitation and temperature scenario. The future temperature increase of 4.8 °C by 2080s (2070–2099) led to prediction of 30.8 % decrease of mixed forest and 75.8 % increase of coniferous forest compared to the baseline forest community. For the baseline evapotranspiration (ET) of 491.5 mm/year, the 2080s ET under the forest community change was 591.1 mm/year, whereas it was 551.8 mm/year with the remaining forest community stationary. The different ET results considering the future forest community clearly affected the groundwater recharge and streamflow in sequence.     

Assessment of the occurrence of climate change and its effects on planting date and growth duration of rainfed wheat in the western and northwestern regions of Iran

In this study, the effect of climate change on planting date and growth duration of rainfed wheat in the west and northwest parts of Iran has been investigated. The occurrence of climate change in the region was first evaluated for the base period (1992–2018) using two nonparametric tests of Mann–Kendall and Sen's slope estimator. Then, the climatic parameters of maximum temperature, minimum temperature and precipitation were simulated under RCP4.5 scenario for the period 2019–2039 based on downscaled output data of the Community Climate System Model (CCSM4) using LARS WG software. The growth period was obtained using a linear multiple regression model, which was selected based on R-square and accounted for 87% of its total variation. The results predicted that the average annual temperature will increase by 2 °C, while the average annual precipitation will increase by 30% by the end of 2039. Planting dates were determined based on two indices combining temperature and precipitation for the base and future periods. The results showed that climate change effects at the 2039 horizon will shorten by 18 days the wheat growth period and the appropriate planting time for rainfed wheat will be reduced by 2–19 days.

     

气候变化对福建省牧草气候生产潜力的影响

以福建省为研究区域,研究牧草生产力与气候条件的关系及其对气候变化的响应.结果表明,近50a来,福建省气温呈现升高趋势,平均每10 a升高0.2℃;年降水量变化总体上呈不显著的增加态势;牧草气候生产潜力随年代的变化呈先减后增的趋势;空间上以厦门地区最高,三明地区最低.降水量对福建省牧草气候生产潜力的影响明显高于气温.若未来温度每降低1℃,降水减少1 mm时,牧草气候生产潜力分别降低318.3 kg·hm~(-2)·a~(-1)和22.7 kg·hm~(-2)a~(-1).     

Evaluation of future climate change impact on snow hydrology for a mountainous watershed of South Korea using SLURP model and NOAA AVHRR images

This study is to evaluate the future potential climate impact on snow hydrology using SLURP model for a 6661.0 km² mountainous watershed of South Korea. For the model test, the NOAA AVHRR images were analyzed to prepare snow-related data of the model. Snow cover areas were extracted using channels 1, 3, and 4, and the snow depth was spatially interpolated using snowfall data of 11 ground meteorological stations. With the snowmelt parameters (snow cover area, snow water equivalent, and snow depth), the model was calibrated for 2 sets (2002–2003, 2004–2005), and verified for 2 sets (1997–1998 and 2001–2002) using the calibrated parameters. The average Nash–Sutcliffe efficiencies during the full year period (December to November) and snowmelt period (December to April) were 0.60 and 0.66, respectively. The future climate data of CCCma CGCM2 SRES A2 and B2 scenarios were adjusted and downscaled using change factor method. By the future impact of climate change, the annual dam inflows were projected to change maximum ?29.3 and ?30.4 % for 2090s A2 scenario and 2030s for B2 scenario, respectively. The future dam inflow increased in winter season (December to February) up to 222.0 %, while other periods decreased up to 54.8 %. The future snowmelt increased in December and January by the future temperature increase of 3.9 °C in minimum. The future snowmelt for the 2 months affected the dam inflows during the winter season.     

Specification of climatic sensitivity of forage maize to climate change

The use of manipulative experiments to study directly the effects of climate change on natural and managed systems is expensive if performed on a large scale: it also relies upon accurate predictions of future climatic conditions. Predictive modelling is less expensive and permits a range of scenarios to be considered but this is only as reliable as the underpinning model.
Predicting the suitability of England and Wales for the cultivation of forage maize under climate change was attempted using an established crop growth model by Muchow et al. (1990) integrated with climate data. The biological and climatic inputs to the model were the thermal requirements for the stages of crop growth, leaf number, leaf area, harvest index, the daily maximum and minimum air temperature, precipitation and solar radiation. These values were obtained from a daily meteorological database for ninety-three sites in England and Wales for the period 1951–80. Model outputs as point values of potential crop yield predicting current production -'baseline'- were statistically validated using actual crop yield data collated from bibliographic analysis. The baseline results indicated that pans of the south-east appeared to be too dry and the north too cold. The model was run again using an artificial sensitivity test (temperature +2°C. precipitation ±10%). Increased precipitation led to a predicted increase in geographical suitability of the UK for forage maize production to the north and west. Under reduced precipitation there was a decrease in suitability in the south-east, possibly owing to moisture stress.     

Decadal changes in the rice-cropping system in the Ayeyarwady Delta using a large archive of satellite imagery from 1981 to 2020

In the last 40 years, the rice-cropping system has considerably changed in the Ayeyarwady Delta. The large archive of satellite imagery provides a history of how land and water resource managements have changed in the face of growing populations, resource demand, and climate change. This study aimed to assess the decadal changes in the rice-cropping system in the Ayeyarwady Delta by using the large archive of satellite imagery for the last 40 years (1981???2020). The long-term NDVI dataset provided various information on rice cultivation. Signal processing techniques were used to detect on the historical changes in the rice-cropping system, and the impact of climate change was assessed by using trend analysis. Until the 1980s, single-cropping of summer rice was dominant in the Delta. To enhance the grain yield of rice, the irrigation facilities were introduced in 1992 under an initiative of the Myanmar government. As a result, the annual cropping intensities increased from 1.087?±?0.390 in the 1980s to 1.422?±?0.499 in the 2010s. The information on historical change in the rice-cropping system would be useful to consider the practical and cost-effective utilization of remaining land and water resources. Moreover, the trend analysis of NDVI time-series showed negative trends in coastal areas. This indicates that the rice production in coastal areas has been constrained by the saline intrusion. The salt-affected areas are expected to expand under future climate change scenarios. Government support is highly required for sustainable rice production in the Delta.

     

Synoptic weather typing and typhoon with an application to Chiayi, Taiwan: potential for future climate change impact analysis

In this study, an automated synoptic weather typing was employed to identity the weather types most likely associated with daily typhoon/typhoon-related heavy rainfall events for Chiayi, Taiwan. The synoptic weather typing was developed using principal components analysis, an average linkage clustering procedure, and discriminant function analysis. The classification results showed that the synoptic weather typing was successful at identifying typhoon-related weather types. Five synoptic weather types (Weather Types 1–5) were identified over the past 11-year period as the primary typhoon-related weather types. These five typhoon-related weather types can capture 34 out of 36 total typhoon-related heavy rainfall days (>50 mm/d) and all nine cases with typhoon-related daily rainfall >200 mm during the period March 1998–December 2008. This result suggests that synoptic weather typing can be useful to identify historical typhoon/typhoon-related heavy rainfall events. Moreover, the method has potential to assess climate change impacts on the frequency/intensity of future typhoon/typhoon-related heavy rainfall events using future downscaled GCM climate data.     

气候变化对甘肃农牧交错带主要粮食作物生产潜力的影响

为探讨热量、降水量及辐射资源变化对甘肃农牧交错带作物气候生产潜力的影响,基于甘肃农牧交错带45个气象站点1971-2020年的逐日气象资料以及主要粮食作物（春小麦、冬小麦和春玉米）生育期资料,利用数量统计分析方法计算3种粮食作物的气候生产潜力。结果表明,近50年来,甘肃农牧交错带春小麦、冬小麦和春玉米生育期内平均气温和降水量均呈上升趋势,太阳辐射量呈下降趋势;光合生产潜力、光温生产潜力和气候生产潜力分别从北到南、东北到西南和南到北呈递减趋势。热量变化对甘肃农牧交错带3种粮食作物的气候生产潜力有正效应,气候生产潜力平均增速分别为32.17、48.11和48.35 kg·hm^-2·a^-1。降水变化对该区域大部分地区春小麦和春玉米气候生产潜力有正效应,气候生产潜力平均增速分别为5.10和7.16 kg·hm^-2·a^-1;降水变化对部分区域冬小麦气候生产潜力产生负效应,气候生产潜力平均降速为0.12 kg·hm^-2·a^-1。辐射变化对该区域大部分地区3种粮食作物的气候生产潜力有负效应,气候生产潜力平均降速分别为1.81、2.35和8.66 kg·hm^-2·a^-1。总体来看,气候资源变化对甘肃农牧交错带大部分地区春小麦、冬小麦和春玉米气候生产潜力表现出正效应,但对临洮、灵台和靖远等地区的春玉米气候生产潜力有负效应。     

Panicum maximum cv. Tanzânia: climate trends and regional pasture production in Brazil

Projected change in forage production under a range of climate scenarios is important for the evaluation of the impacts of global climate change on pasture‐based livestock production systems in Brazil. We evaluated the effects of regional climate trends on Panicum maximum cv. Tanzânia production, predicted by an agro‐meteorological model considering the sum of degree days and corrected by a water availability index. Data from Brazilian weather stations (1963–2009) were considered as the current climate (baseline), and future scenarios, based on contrasting scenarios in terms of increased temperature and atmospheric CO₂ concentrations (high and low increases), were determined for 2013–2040 (2025 scenario) and for 2043–2070 (2055 scenario). Predicted baseline scenarios indicated that there are regional and seasonal variations in P. maximum production related to variation in temperature and water availability during the year. Production was lower in the Northeast region and higher in the rainforest area. Total annual production under future climate scenarios was predicted to increase by up to 20% for most of the Brazilian area, mainly due to temperature increase, according to each climate model and scenario evaluated. The highest increase in forage production is expected to be in the South, Southeast and Central‐west areas of Brazil. In these regions, future climate scenarios will not lead to changes in the seasonal production, with larger increases in productivity during the summer. Climate risk is expected to decrease, as the probability of occurrence of low forage productions will be lower. Due to the predicted increase in temperature and decrease in rainfall in the Northeast area, P. maximum production is expected to decrease, mainly when considering scenarios based on the PRECIS model for the 2055 scenario.     

Modelling of groundwater recharge potential from irrigated paddy field under changing climate

Groundwater recharge from irrigated paddy field under various projected climate change scenarios was assessed using HYDRUS-1D model. Recharge flux, root water uptake, evaporation and surface runoff were simulated on daily time step for the growing period of paddy. Crop evapotranspiration and effective rainfall during the simulation period were estimated to be 301.9 and 269.4 mm, respectively. Cumulative bottom flux, root water uptake, evaporation and surface runoff were 69.2, 23.2, 30.8 and 0.0 cm for sandy loam and 37.2, 23.0, 30.8 and 0.7 cm for clay loam soils, respectively. Simulation results showed that the groundwater recharge potentials in sandy loam and clay loam soils with paddy crop are 69.2 and 37.2 cm, respectively. Cumulative recharge under various climate change scenarios from paddy field varied from 63.9 to 74.4 cm, 33.7 to 39.8 cm, 29.3 to 35.4 cm and 27.1 to 34.3 cm from land units A1 (sandy loam), B1 (clay loam with slight salinity), C1 (clay loam with moderate saline and slight sodic) and D1 (clay loam with strong saline and sodic), respectively. Cumulative recharge flux under the scenarios in which increase in relative humidity along with decrease in duration of sunshine hours was associated with rise in average temperature and wind speed, groundwater recharge would increase by 7.4 %. Cumulative recharge flux under the scenarios which were based on rise in temperature along with the increase in rainfall, groundwater recharge would increase by 0.2–3.9 %. Simulation results also showed that cumulative recharge would decrease under all those scenarios, which were based on rise in temperature only.     

Assessment of rice hydraulic loading impacts on groundwater and salinity levels

This paper describes the impact of rice hydraulic loading (percentage area under rice crop) on groundwater levels and salinity in the Murrumbidgee irrigation area (MIA), Australia using a MODFLOW-based modelling approach. The model simulations show that the groundwater levels will be in equilibrium after a fall of approximately 1 m under most of the areas, however, the groundwater salinity levels will rise by more than 1,000 μs/cm in most parts of irrigation area. If the rice growing area is reduced by 50 and 75%, there can be a net decline in groundwater levels during the first 2 years and then a new quasi-equilibrium will be established. To downscale these results at the farm level, SWAGMAN Farm model in conjunction with groundwater outflow rates obtained from a three-dimensional MODFLOW model was applied for determining net recharge rates under rice for different areas within the MIA. The highest net recharge during 2005–2006 season was 0.84 ML/ha (84 mm) in parts of the irrigation system, whereas the average net recharge due to rice hydraulic loading for the whole MIA during 2005–2006 season was estimated as 0.34 ML/ha (34 mm).     

辽宁省玉米种植农业气候要素分析及精细化气候区划研究

根据农业气候条件的地区差异，研究辽宁省玉米种植气候区划的变化，规划辽宁省玉米种植和促进辽宁省玉米产业的可持续发展。研究结果表明，1961～2018年辽宁省农业气候资源在时间上呈现“降水减少、积温升高”的暖干化趋势。空间分布上呈现地域性差异，对辽宁省玉米气候区划因子进行指标划分，通过GIS得到近58年辽宁省玉米气候区划，分为最适宜区、适宜区和基本适宜区。从1961～1990年、1971～2000年、1981～2010年，基本适宜区和最适宜区呈现先增加再减小的趋势，适宜区呈现先减小再增加的趋势。     

Water balance characteristics of Kashima plateau basins assuming variable areas of underground catchments

Agricultural water use on upland fields depends mainly on precipitation and irrigation by small wells in the Kashima plateau basins. To establish a stable supply of water for irrigated upland fields, an evaluation of water-cycle mechanisms on an arable plateau near plain lakes is important. Previous research suggests that groundwater catchments do not necessarily coincide with the corresponding surface catchments in the plateau basins. However, a physical mechanism of groundwater movement has not yet been clearly demonstrated. In this paper, therefore, we aimed to estimate the areas of groundwater catchments that did not coincide with their corresponding surface catchments, by observing groundwater flow in boreholes and by evaluating water balances of four small basins on the Kashima plateau. As a result, hydrological and groundwater observations in the Kashima-Kohoku basin showed: (1) the groundwater catchment was larger than the surface catchment, as inferred from continuous groundwater observations and the observed directions of groundwater flow, (2) groundwater potential may change after intensive rains, especially after precipitation events of more than 50 mm, and (3) estimates of the long-term water balance confirmed that groundwater flowed into the surface catchment from the outside. The area of the Kashima-Kohoku groundwater catchment was 1.3–2.4 times the area of the surface catchment. Furthermore, the same result was obtained for two other basins.     

茶叶腌制过程中亚硝酸盐和游离氨基酸含量的动态变化分析

本实验以绿毛茶为原料进行腌制,分别对其安全性指标--亚硝酸盐含量,营养风味指标--游离氨基酸含量进行动态研究,结果发现:在3个月的腌制期间,亚硝酸盐与游离氨基酸的动态含量变化呈现相反的变化趋势;亚硝酸盐含量变化呈两度下降两度上升的总体下降趋势;游离氨基酸的含量呈三度上升三度下降的总体上升趋势.茶叶腌制后,并没有呈现一般果蔬类制品在腌制前期,亚硝酸盐含量快速上升的现象,却呈现亚硝酸盐含量总体下降的变化趋势,且远低于蔬菜<4 mg/g,酱腌菜<20 mg/g的国家安全控制标准.而游离氨基酸含量与果蔬腌制品一样呈现总体上扬的变化趋势.     

Climate change impacts on agriculture and irrigation in the Lower Mekong Basin

According to hydrological simulations by the Mekong River Commission, average annual flow of the Mekong will not change significantly despite climate change. However, they projected increased variability in wet and dry season flows, which will tend to increase the flood and drought risks to crops. To learn the implications of climate change for rice farming in the Lower Mekong Basin (LMB), a lower part of the Basin from China-Lao PDR border to the South China Sea, climate and hydrological figures related to rice production were compared in between the baseline in 1985–2000 and the climate change scenario in 2010–2050. Special attention was given to their 10 and 90 % exceedance values, which are rough equivalence of 10 and 90 % cumulative probabilities, to see changes in the frequency and extent of extreme weather events. Major findings of this study include the followings: (1) evapo-transpirations will increase in both average and 90 % cumulative probability values, raising irrigation demand. (2) Deviation of the annual rainfall will become larger, causing water shortage in reservoirs more frequently in the future. (3) The transplanting date of rain-fed rice will be delayed more likely due to insufficient precipitation in the early wet season, which may result in decreasing rice production. (4) Longer dry spells will be observed during the wet season, raising the drought risk to rain-fed rice. (5) These changes will be generally observed across the LMB, while the extent of the changes varies among regions.

     

1971-2017年陇中地区气候变化及其对旱地春小麦产量的影响

为了解不同生育阶段气候变化对旱地春小麦产量的影响,利用陇中地区1971-2017年逐日气温和降水量,运用APSIM模型模拟春小麦生育期和产量,对近47年来该地区气候变化特征及其与春小麦产量的相关性进行了分析。结果表明,陇中地区年降水量按4.639 mm·10a^-1的速率显著减少,春小麦全生育期降水量按1.304 mm·10a^-1的速率减少,8个生育阶段的降水变化趋势不同,其中灌浆-成熟期的降水量下降幅度最大,倾向率为-2.995 mm·10a^-1;分蘖-拔节期的降水量有明显的上升趋势,倾向率1.855 mm·10a^-1。旱地春小麦全生育期和各生育阶段的日均温、日均最高温和日均最低温都呈上升趋势,并且日均最低温的上升幅度要大于日均最高温。经相关分析,旱地春小麦全生育期降水量和日均最高温与产量分别呈极显著和显著相关;拔节-孕穗期和灌浆-成熟期降水量与产量的相关性分别达显著和极显著水平,拔节-孕穗期和灌浆-成熟期日均温与产量均呈极显著相关,拔节-孕穗期和灌浆-成熟期的日均最高温与产量分别呈显著相关和极显著相关。     

Climate change impacts on agriculture and irrigation in the Lower Mekong Basin

According to hydrological simulations by the Mekong River Commission, average annual flow of the Mekong will not change significantly despite climate change. However, they projected increased variability in wet and dry season flows, which will tend to increase the flood and drought risks to crops. To learn the implications of climate change for rice farming in the Lower Mekong Basin (LMB), a lower part of the Basin from China-Lao PDR border to the South China Sea, climate and hydrological figures related to rice production were compared in between the baseline in 1985–2000 and the climate change scenario in 2010–2050. Special attention was given to their 10 and 90 % exceedance values, which are rough equivalence of 10 and 90 % cumulative probabilities, to see changes in the frequency and extent of extreme weather events. Major findings of this study include the followings: (1) evapo-transpirations will increase in both average and 90 % cumulative probability values, raising irrigation demand. (2) Deviation of the annual rainfall will become larger, causing water shortage in reservoirs more frequently in the future. (3) The transplanting date of rain-fed rice will be delayed more likely due to insufficient precipitation in the early wet season, which may result in decreasing rice production. (4) Longer dry spells will be observed during the wet season, raising the drought risk to rain-fed rice. (5) These changes will be generally observed across the LMB, while the extent of the changes varies among regions.     

Assessing the impact of climate change on the land hydrology in Taiwan

The gradually increased temperature resulting from the enhanced greenhouse effects has been found to be an important factor of changes to the global climate which in turn might significantly affect the Earth's hydrological cycles. The possible outcomes of warming climate are changes of precipitation, surface runoff, evapotranspiration, and frequency of extreme weather events, such as floods and droughts. However, such changes at the global scale may not reflect the variations on a regional scale, and more so at the local scale. In this study, a physically based water balance model was applied to study the impact of climate change on the land hydrology, focusing on trends of surface runoff, evapotranspiration, and infiltration in Taiwan. Model forcing of composite temperatures and precipitations were generated by a weather generation model in association with nine climate change scenarios, including outputs of equilibrium experiments and special reports on emissions scenarios, from the IPCC. Although discrepancies among different climate change scenarios are significant, the trend of more extreme precipitations and surface runoffs were observed in most scenarios' runs. The increase of evapotranspiration in both wet and dry seasons is persistent among different scenarios throughout the island due to the projected consistently higher temperature. Although the trends of infiltration for wet and dry seasons are opposite in curtain scenarios, a decreased yearly infiltration was found in most cases as the result of increased precipitation intensity and more evapotranspiration. Timely adaption measures for water resources managements and natural hazard mitigations are required to face these changes of land hydrology components under changing climate.