Decrease In Evapotranspiration Research Articles

Modeling evapotranspiration changes with managing Japanese cedar and cypress plantations

Examining changes in evapotranspiration with forest management is one starting point for comprehensively understanding the impacts of forest management on water resources and forest resilience. This study builds on our previous work and develops a practical model that predicts changes in evapotranspiration with the management of Japanese cedar and cypress plantations. The model has distinct features that it requires only stem density, mean diameter at breast height, and basic meteorological data as inputs. This study first confirms that the model predicts annual evapotranspiration for cedar and cypress with relatively small errors (approximately 60 mm at the maximum). Next, this study shows that the model predicts changes in annual evapotranspiration with thinning and clearcutting of cedar and cypress with small errors (the mean absolute error of 86 mm). This study then demonstrates that coupling the model and yield tables enables prediction of annual evapotranspiration for different management scenarios and then the assessment of policy recommendations. Indeed, our model prediction suggests that the decrease in annual evapotranspiration with cedar and cypress aging is seemingly much smaller than that assumed in existing policy recommendations. Our model also suggests that the decrease in annual evapotranspiration with aging can more than triple by thinning at a rate of 50%, although this suggestion should be tested by future observation studies. The model is applicable only to Japanese cedar and cypress plantations under Japan’s meteorological conditions, but similar models for other mono-specific plantations can be developed. This study will thus inspire forest scientists to develop models that assist policymaking for other species in other areas.

Integrating of settlement area in urban and forest area of Bartin with climatic condition decision for managements

Thornthwaite climate classification indices are essential to interpret climate types in Bartin City, simplifying calculation process and interpretation of climatological water balance by forests. Thus, we aimed to develop a climatological water balance by the Thornthwaite method, as well as climatic characterization using the indices proposed by Thornthwaite for Bartin (including measurement points are Amasra, Arit, Hasankadi, Kozcagiz, Kurucasile, Ulus, Ulus Cubukeli, Ulus Ceyupler Koyu). We used historical series of climate data from all 15 metrological stations of Bartin between 1988 and 2019, which were divided into measurements regions. Air temperature and precipitation were collected on a daily scale. Precipitation and potential evapotranspiration data allowed calculating water balance by the Thornthwaite method. We characterized all locations as wet and dry using aridity indices proposed by Thornthwaite. Maps were generated from climate indices of Bartin using kriging interpolation method with spherical model, one neighbor, and 0.25° resolution. The measurement regions showed different patterns regarding water balance components and humidity index. Humidity index had a mean of 16.97. The prevailing climate in Bartin is moist subhumid. Bartin has two well-defined periods during the year: a dry and a rainy period. Three climate types predominate in Bartin and, according to the Thornthwaite classification, are humid, moist subhumid, and dry subhumid. Water characterization in Bartin showed 123.67 mm year−1 of water surplus, 79.7 mm year−1 of water deficit, and 1003.9 mm year−1 of potential evapotranspiration. Water deficit and potential evapotranspiration decrease as latitude increases.

Modeling runoff response to land-use changes using the SWAT model in the Mundaú watershed, Brazil

Land-use change has a significant influence on runoff process of any watershed, and the deepening of this theme is essential to assist decision making, within the scope of water resources management. The study was conducted for Mundaú River Basin (MRB) using the Soil and Water Assessment Tool (SWAT) model. The study aims to assess the issue of land-use change and its effect on evapotranspiration, surface runoff, and sediment yield. Input data like land use, topography, weather, and soil data features are required to undertake watershed simulation. Two scenarios of land use were analyzed over 30 years, which were: a regeneration scenario (referring to use in the year 1987) and another scene of degradation (relating to use in the year 2017). Land use maps for 1987 and 2017 were acquired from satellite images. Overall, during the last three decades, 76.4% of forest was lost in the MRB. The grazing land increased in 2017 at a few more than double the area that existed in 1987. Changes in land use, over the years, resulted in an increase of about 37% in the water yield of MRB. Changes have led to increased processes such as surface runoff and sediment yield and in the decrease of evapotranspiration. The spatial and temporal distribution of land use controls the water balance and sediment production in the MRB.

Olive tree irrigation as a climate change adaptation measure in Alentejo, Portugal

Climate change projections for Southern Europe reveal warming and drying trends for the upcoming decades, bringing important challenges to Portuguese olive orchards in particular. We analyzed irrigation as an adaptation measure to ensure the future sustainability of olive tree yields in Alentejo, the main olive producing area in Portugal. A dynamic crop model was used to simulate olive tree yields over the baseline (1981–2005) and two future scenarios (RCP4.5 and RCP8.5, 2021–2080), using a 4 member-ensemble of state-of-the-art climate model chains. Climate change projections point to an increase in mean temperature (of up to 2 °C by 2080) and potential evapotranspiration (40−50 mm), while a decrease in precipitation (-80 to −90 mm) and actual evapotranspiration (-50 to −70 mm), under both future scenarios. Future yield decreases 15–20% (for RCP4.5 and RCP8.5) and accumulated losses can reach -8 t/ha to −10 t/ha by 2080. This decrease is due to enhanced heat and water stress under future climate conditions. As an adaptation measure, irrigation was simulated, but only applied at a certain water stress level. The results indicate higher yields due to this adaptation strategy, in range with the present values (±1%), thus alleviating the projected yield decreases in the future. The amount of water required for irrigation ranges from 60 to 85 mm, depending on the RCP, which corresponds to 0.6–1 times the projected decrease in precipitation. However, this value can reach up to 2 times for one climate model chain. We conclude that while irrigation is a feasible adaptation measure against the threats of climate change in Alentejo olive orchards, this strategy may be threatened by the scarcity of water resources. Outlining appropriate, timely and cost-effective adaptation measures is critical for the sustainability of both the environment and the Alentejo olive sector.

Streamflow into Beijing and Its Response to Climate Change and Human Activities over the Period 1956–2016

Streamflow is likely affected by climate change and human activities. In this study, hydro-meteorological data from six rivers upstream of Beijing, namely, the Yongdinghe, Baihe, Heihe, Chaohe, Juhe, and Jumahe Rivers, were analyzed to quantify the spatial and temporal variability of streamflow and their responses to climate change and human activities over the period of 1956–2016. The Mann–Kendall test and moving t-test were used to detect trends and changing points of the annual streamflow. Results showed that the streamflow into Beijing experienced a statistically significant downward trend (p < 0.05), abruptly changing after the early 1980s, owing to climate and human effects. The climate elasticities of the streamflow showed that a 10% decrease in precipitation would result in a 24.5% decrease in total streamflow, whereas a 10% decrease in potential evapotranspiration would induce a 37.7% increase in total streamflow. Human activities accounted for 87% of the reduction in total streamflow, whereas 13% was attributed to climate change. Lastly, recommendations are provided for adaptive management of water resources at different spatial scales.

Impact of cover crop on corn–soybean productivity and soil water dynamics under different seasonal rainfall patterns

AbstractThe effect of cover crop (CC) on soil water balance and agricultural production is closely related to rainfall amount and distribution in rainfed cropping systems. This study used the root zone water quality model, RZWQM2, calibrated and validated with 4‐yr field measurements to predict the effect of planting a winter wheat (Triticum aestivum L.) CC in a no‐till rainfed corn (Zea mays L.)–soybean (Glycine max L.) rotation on soil water balance, crop yield, and grain water‐use efficiency (WUE) in northeast Mississippi. Seasonal rainfall for 80 consecutive years (1938–2017) was classified as ‘wet,’ ‘normal,’ and ‘dry’ years using frequency analysis, and the data sets matched chronologically to wheat, corn, and soybean growth periods were used as an input parameter in RZWQM2 simulations. During autumn and spring (early October to early April), the CC reduced deep drainage by 69 (11%), 53 (15%), and 51 mm (21%) in wet, normal, and dry years, respectively. Averaged across 40 yr, the CC decreased surface evaporation by 64 (32%) and 38 mm (24%) for corn and soybean growth periods, respectively. Wheat CC also improved soil water storage in early crop growth period during April–June in any of the three rainfall patterns. Regardless of rainfall patterns, the increase in WUE can be attributed to a decrease in evapotranspiration during cash crop period without sacrificing cash crop yield in the CC system. Introducing CC into cropping systems is beneficial to reduce annual deep drainage and evaporation while maintaining higher crop yields under different rainfall patterns.

Land Use/Land Cover Changes over a District in Northern India using Remote Sensing and GIS and their Impact on Society and Environment

Abstract This study focuses on exploring changes in Land Use and Land Cover (LULC) over Baramulla district of Kashmir using remote sensing and Geographic Information System (GIS). Linkage of LULC with evapotranspiration and precipitation is also explored in this paper. LULC were categorised into dense forest, sparse forest, water body and other classes by using geospatial satellite data from Landsat for the years 1979, 2001 to 2018. The dense forest and water body show decrease in extent from 1979 to 2018. A decrease of about 27 % has been reported from 1979 to 2018 in dense forest. Furthermore, water body shows a reduction of about 36% during the same time span. Significant changes in dense forest and water body affected the water cycle of the region. Reduction in dense forest and water body resulted in significant decrease in evapotranspiration which caused reduction in precipitation over the study area. Reduced precipitation over study area caused conversion from agriculture to horticulture. Increase of about 55% in horticulture has been reported with decrease of about 54% in agriculture over study area. Evapotranspiration from reanalysis shows coherent variation with precipitation from India Meteorological Department (IMD) gridded product. A decadal decrease of about 0.5% in evapotranspiration resulting in decrease of about 0.38% in precipitation over study area is reported. Increased horticulture causes increase in black carbon due to increased biomass which results in increased warming over study area. Changes reported in this study may cause a significant socioeconomic and environmental impact over Baramulla.

Irrigation‐Induced Potential Evapotranspiration Decrease in the Heihe River Basin, Northwest China, as Simulated by the WRF Model

AbstractEvapotranspiration occurs via land‐atmosphere coupling. To understand the impacts of irrigation on local potential evapotranspiration, we carried out a couple of simulations with the Weather Research and Forecast (WRF) model, where an irrigation scheme was incorporated, for the irrigated area in the middle reaches of the Heihe River, Northwest China. By comparing the irrigation simulation (hereafter, the IRRG case) with the simulation excluding irrigation (hereafter, the NATU case), we found that irrigation may lead to a decrease in reference evapotranspiration (ET0) during the growing season (May to September), which is a metric of potential evapotranspiration, by approximately 1.05 mm d−1, accounting for approximately 19% of NATU ET0. The ET0 in the IRRG is closer to the ground measurements than the NATU ET0, with a root‐mean‐square error of 0.75 mm d−1 in the IRRG and 1.86 mm d−1 in the NATU cases. Meanwhile, irrigation leads to an actual evapotranspiration (ETa) increase of approximately 2.1 mm d−1 for croplands. Such an asymmetric relationship between ET0 decrease and ETa increase was found over the irrigated croplands. The ET0 decrease was mainly induced by the moistening and cooling effects of irrigation through intensified evapotranspiration and reduced sensible heat. This study highlights the importance of considering land‐atmosphere coupling when assessing the impacts of climatic change on irrigation water requirements.

Effects of dynamic land use/land cover change on water resources and sediment yield in the Anzali wetland catchment, Gilan, Iran

Land use/land cover (LULC) changes strongly affect catchment hydrology and sediment yields. The current study aims at analyzing the hydrological consequences of dynamic LULC changes in the Anzali wetland catchment, Iran. The Soil and Water Assessment Tool (SWAT 2012) model was used to assess impacts on evapotranspiration, water yield, and sediment yield. Two model runs were performed using static and dynamic LULC inputs to evaluate the effects of LULC change between 1990 and 2013. For the static model, the LULC map of 1990 was used, whereas for the dynamic model, a gradual change of the LULC distribution was interpolated from 1990, 2000, and 2013 LULC data. The major LULC changes were identified as an increase of agricultural area by 7% of the catchment area and a decrease of forest coverage by 6.8% between 1990 and 2013. At the catchment scale, the differences in the long-term mean annual values for the main water balance components and sediment yield were smaller than 10 mm (<2.8%) and 3 t/km2 (<2.6%), respectively. However, at the sub-basin scale the increase of agricultural land use resulted in an increase of evapotranspiration, water yield, and sediment yield by up to 8.3%, 7%, and 169%, respectively, whereas urban expansion led to a decrease of evapotranspiration, water yield, and sediment yield by up to −3.5%, −2.3%, and −9.4%. According to the results of the monthly time scale analysis, the most significant impact of LULC changes occurs during the dry season months, when the increase of irrigation agriculture results in an increase in water discharge and sediment loads to the Anzali wetland. Overall, the results showed that the implementation of dynamic LULC change into the SWAT model could be adopted as a planning tool to manage LULC change of the Anzali wetland catchment in the future.

Attribution analyses of evapotranspiration and gross primary productivity changes in Ziya-Daqing basins, China during 2001–2015

Evapotranspiration (ETa) and gross primary productivity (GPP) are two of the key flux indices in a basin system. This study investigated the evolutions of ETa and GPP and the contributions of climate variables and vegetation index over multiple land cover types, simulated by the VIP model (Vegetation Interfaces Processes, RS version) with Terra-Modis 250 m Normalized Difference Vegetation Index (NDVI) dataset in the Ziya-Daqing basins (ZDB), China, during 2001–2015. The nonparametric Mann-Kendall test was used to analyze the changes in ETa and GPP. Contributions to the variations of ETa and GPP were explored using a differential equation method. The analyses revealed that ETa and GPP were high in the eastern plain, and spatial distributions were mainly associated with distributions of the major land-cover types. ETa and GPP showed positive trends in the western Taihang Mountains and negative trends in the eastern plain region. The annual ETa and GPP increased from 2001 to 2015 in most land-use types except cropland and urban. The decreases in ETa and GPP were primarily attributed to solar dimming in cropland and urban. The increases in ETa and GPP mainly occurred in the natural land-cover types (e.g., mixed forest and grassland) as a tradeoff between the positive effect of greening and the negative effect of declined radiation. In ZDB, the contributions of net radiation, air temperature, wind speed, and leaf area index to the change in ETa were − 0.681%, − 0.379%, − 0.032%, and 1.442%, respectively. The contributions of net short-wave radiation, air temperature, relative humidity, and fraction of photosynthetically active radiation to the change in GPP were − 2.411%, 0.085%, − 0.020%, and 10.224%, respectively. Thus, the “greening” was the major reason for ETa and GPP increases in natural vegetations, whereas solar dimming was the major reason for ETa and GPP decreases in cropland.

Regional hydro-climatic changes in the Southern Amazon Basin (Upper Madeira Basin) during the 1982–2017 period

Study regionUpper Madeira Basin (975,500 km2) in Southern Amazonia, which is suffering a biophysical transition, involving deforestation and changes in rainfall regime. Study focusThe evolution of the runoff coefficient (Rc: runoff/rainfall) is examined as an indicator of the environmental changes (1982–2017). New hydrological insights for the regionAt an annual scale, the Rc at Porto Velho station declines while neither the basin-averaged rainfall nor the runoff change. During the low-water period Rc and runoff diminish while no changes are observed in rainfall. This cannot be explained by increase of evapotranspiration since the basin-averaged actual evapotranspiration decreases. To explain the decrease of Rc, a regional analysis is undertaken. While the characteristic rainfall-runoff time-lag (CT) at Porto Velho basin is estimated to 60 days, CT is higher (65–75 days) in the south and lower (50 days) over the Amazon-Andes transition regions. It is found that 1) the southern basin (south of 14 °S) best explains low-level Porto Velho runoff, 2) in the south, rainfall diminishes and the frequency of dry days increases. Both features explain the diminution of the runoff and the Rc in Porto Velho. Moreover, the increasing dryness in the south compensates for the rainfall and frequency of wet days (>10 mm) increase north of 14 °S and explains the lack of basin-averaged rainfall trends of the upper Madeira basin.

Increased water yield and altered water partitioning follow wildfire in a forested catchment in the western United States

AbstractAs wildfires in much of the western United States increase in size, frequency, and severity, understanding the impact of these fires on water yield from forested headwater basins is essential to successful management of water resources. The current study examines the changes in partitioning of the hydrologic cycle in the Mill Creek Basin that follow the Chippy Creek Fire in Montana, USA, due to alterations to the vegetative regime. The analysis utilizes remote sensing‐based vegetation indices and evapotranspiration, a model‐interpolated precipitation product, and discharge data to assess annual water budgets and vegetative regimes in the Mill Creek Basin. After being almost 90% burned in the Chippy Creek Fire, vegetation in the catchment has shifted from almost exclusively mixed conifer forest to sagebrush scrubs and grasses. This shift in vegetation is accompanied by abrupt shifts in partitioning of the water budget, resulting in an altered ecohydrologic regime. Post‐fire, evapotranspiration decreases annually by 250 mm (46%), and evaporative fraction decreases by 0.53. However, evapotranspiration product biases may overestimate this decrease from pre‐ to post‐fire. This decrease in evapotranspiration results in an annual increase in streamflow of 136 mm, a 21% increase in the runoff ratio, and a 140% increase in water yield. These changes to the water budget are consistent for 10 years post‐fire and show no trend towards pre‐fire values during the study period. Results will help inform planning and management of water resources downstream of forested catchments that have been impacted by wildfire.

Quantifying the impact of climate variables on reference evapotranspiration in Pearl River Basin, China

ABSTRACTThe impact of climate variables on monthly reference evapotranspiration (ETo) is a critical issue in water resources management and irrigation planning. The spatio-temporal contribution of climate variables to ETo in the Pearl River Basin (PRB), China, from 1960 to 2016 were calculated based on sensitivity and relative change of each climatic variable. The results show that annual ETo total decreased by 1.64% and diminished in magnitude from the southeast to the northwest. Sunshine duration, wind speed and relative humidity decreased by 15.5%, 7.4%, and 4.0%, respectively, while average temperature increased by 4.25%. The ETo showed a positive sensitivity to all variables except relative humidity, which showed a negative sensitivity. Sunshine duration had the highest contribution of −4.26%, and the overall decrease in ETo was mainly caused by the declines in sunshine duration and wind speed, which offset the positive impact of rises in average temperature and reduction in relative humidity.

Drought- and heat-induced shifts in vegetation composition impact biomass production and water use of alpine grasslands

Future climate change scenarios predict more frequent and intense droughts for Alpine grasslands, primarily driven by altered precipitation regimes and increased evapotranspiration. The grassland community is expected to adjust to decreasing soil moisture and increasing potential evapotranspiration, optimising water use according to the individual strategies and competitive interactions between the present species. Here, we show the reaction of an intensive Alpine grassland to drought and heat at community and plant functional group levels by using small high-precision lysimeters, as well as how the community adapts by a shift from legumes to grasses after a severe drought. Drought and heating experiments revealed a decrease in evapotranspiration as well as in biomass production only at the highest drought intensity (i.e. soil water potential reaching the permanent wilting point). At plant functional group level, an upscaling from leaf porometer measurements revealed a similar decrease of transpiration for legumes and grasses, but differences between them in the rewetting phase. Legumes were strongly affected by drought and showed a low regrowth during the recovery, while grasses enhanced transpiration and even exceeded biomass productivity of the moist treatment. This imbalance between functional groups caused a shift from legumes to grasses in the grassland community. We conclude that drought-induced community re-assemblage of Alpine grasslands enhances water use efficiency.

Rogation ceremonies: a key to understanding past drought variability in northeastern Spain since 1650

Abstract. In the northeast of the Iberian Peninsula, few studies have reconstructed drought occurrence and variability for the pre-instrumental period using documentary evidence and natural proxies. In this study, we compiled a unique dataset of rogation ceremonies – religious acts asking God for rain – from 13 cities in the northeast of Spain and investigated the annual drought variability from 1650 to 1899 CE. Three regionally different coherent areas (Mediterranean, Ebro Valley, and Mountain) were detected. Both the Barcelona and the regional Mediterranean drought indices were compared with the instrumental series of Barcelona for the overlapping period (1787–1899), where we discovered a highly significant and stable correlation with the Standardized Precipitation Index of May with a 4-month lag (r=-0.46 and r=-0.53; p&lt;0.001, respectively). We found common periods with prolonged droughts (during the mid and late 18th century) and extreme drought years (1775, 1798, 1753, 1691, and 1817) associated with more atmospheric blocking situations. A superposed epoch analysis (SEA) was performed showing a significant decrease in drought events 1 year after the volcanic events, which might be explained by the decrease in evapotranspiration due to reduction in surface temperatures and, consequently, the higher availability of water that increases soil moisture. In addition, we discovered a common and significant drought response in the three regional drought indices 2 years after the Tambora volcanic eruption. Our study suggests that documented information on rogation ceremonies contains important independent evidence to reconstruct extreme drought events in areas and periods for which instrumental information and other proxies are scarce. However, drought index for the mountainous areas (denoted Mountain later in the text) presents various limitations and its interpretation must be treated with caution.

Importance of Surface Roughness for the Local Biogeophysical Effects of Deforestation

AbstractDeforestation influences surface properties such as surface roughness, resulting in changes in the surface energy balance and surface temperature. Recent studies suggest that the biogeophysical effects are dominated by changing roughness, and it remains unclear whether this can be reconciled with earlier modeling studies that highlighted the importance of a reduction of evapotranspiration in the low latitudes and a reduction of net shortwave radiation at the surface in the high latitudes. To clarify this situation, we analyze the local effects of deforestation on surface energy balance and temperature in the MPI‐ESM climate model by performing three separate experiments: switching from forest to grass all surface properties, only surface albedo, and only surface roughness. We find that the locally induced changes in surface temperature are dominated by changes in surface roughness for the annual mean, the response of the diurnal amplitude, and the seasonal response to deforestation. For these three quantities, the results of the MPI‐ESM lie within the range of observation‐based data sets. Deforestation‐induced decreases in surface roughness contribute substantially to winter cooling in the boreal regions and to decreases in evapotranspiration in the tropics. By comparing the energy balance decompositions from the three experiments, the view that roughness changes dominate the biogeophysical consequences of deforestation can be reconciled with the earlier studies highlighting the relevance of evapotranspiration.

Trends and controls on water-use efficiency of an old-growth coniferous forest in the Pacific Northwest

At the ecosystem scale, water-use efficiency (WUE) is defined broadly as the ratio of carbon assimilated to water evaporated by an ecosystem. WUE is an important aspect of carbon and water cycling and has been used to assess forest ecosystem responses to climate change and rising atmospheric CO2 concentrations. This study investigates the influence of meteorological and radiation variables on forest WUE by analyzing an 18 year (1998–2015) half-hourly time series of carbon and water fluxes measured with the eddy covariance technique in an old-growth conifer forest in the Pacific Northwest, USA. Three different metrics of WUE exhibit an overall increase over the period 1998–2007 mainly due to an increase in gross primary productivity (GPP) and a decrease in evapotranspiration (ET). However, the WUE metrics did not exhibit an increase across the period from 2008 to 2015 due to a greater reduction in GPP relative to ET. The strength of associations among particular meteorological variables and WUE varied with the scale of temporal aggregation used. In general, vapor pressure deficit and air temperature appear to control WUE at half-hourly and daily time scales, whereas atmospheric CO2 concentration was identified as the most important factor controlling monthly WUE. Carbon and water fluxes and the consequent WUE showed a weak correlation to the Standard Precipitation Index, while carbon fluxes were strongly dependent on the combined effect of multiple climate factors. The inferred patterns and controls on forest WUE highlighted have implications for improved understanding and prediction of possible adaptive adjustments of forest physiology in response to climate change and rising atmospheric CO2 concentrations.

Changes in vegetation and surface water balance at basin-scale in Central China with rising atmospheric CO2

Elevated atmospheric CO2 concentration alters vegetation growth and composition, increases plant water use efficiency (WUE), and changes surface water balance. These changes and their differences between wet and dry climate are studied at a mid-latitude experiment site in the Loess Plateau of China. The study site, the Jinghe River basin (JRB), covers an area of 43,216 km2 and has a semiarid climate in the north and a semi-humid climate in the south. Two simulations from 1965 to 2012 are made using a site-calibrated Lund–Potsdam–Jena dynamic global vegetation model: one with the observed rise of the atmospheric CO2 from 319.7–391.2 ppmv, and the other with a fixed CO2 at the level of 1964 (318.9 ppmv). Analyses of the model results show that the elevated atmospheric CO2 promotes growth of woody vegetation (trees) and causes a 6.0% increase in basin-wide net primary production (NPP). The NPP increase uses little extra water however because of higher WUE. Further examination of the surface water budget reveals opposite CO2 effects between semiarid and semi-humid climates in the JRB. In the semiarid climate, plants sustain growth in higher CO2 because of the higher level of intracellular CO2 and therefore WUE, thus consuming more water and causing a greater decrease of surface runoff than in the fixed-lower CO2 case. In the semi-humid climate, NPP also increases but by a smaller amount than in the semiarid climate. Plant transpiration (ET) and total evapotranspiration (E) decrease in the elevated CO2 environment, yielding the increase of runoff. This asymmetry of the effects of elevated atmospheric CO2 exacerbates drying in the semiarid climate and enhances wetness in the semi-humid climate. Furthermore, plant WUE (=NPP/ET) is found to be nearly invariant to climate but primarily a function of the atmospheric CO2 concentration, a result suggesting a strong constraint of atmospheric CO2 on biophysical properties of the Earth system.

Features of the balance structure formation of groundwater withdrawal and its effect on river flow at a subsoil water level drawdown

The balance structure of the pumpage sourses of riverside water-intakes, developing a subsoil aquifer or intermediate water that hydraulically interacts with it, can show the effect of the processes of water balance adjustment in the unsaturated zone to the accompanying subsoil water level drawdown. In this case, because of the shallow depth to subsoil water, its level drop due to water withdrawal causes a decrease in evapotranspiration and an increase in groundwater infiltration recharge. These processes have their effect on the balance structure of usable water resources as components of natural and involved resources and reduce the impact of groundwater pumping on river flow. Analysis of the operational data of the Sudogda waterintake in Vladimir oblast and geohydrological modeling were used to evaluate variations of the groundwater evaportanspiration losses and infiltration recharge and their role in the water balance structure of reserves of a field and in the impact of groundwater withdrawal on river flow.

Spatio-temporal patterns of drought evolution over the Beijing-Tianjin-Hebei region, China

Spatio-temporal patterns of drought from 1961 to 2013 over the Beijing-Tianjin-Hebei (BTH) region of China were analyzed using the Palmer Drought Severity index (PDSI) based on 21 meteorological stations. Overall, changes in the mean-state of drought detected in recent decades were due to decreases in precipitation and potential evapotranspiration. The Empirical Orthogonal Functions (EOF) method was used to decompose drought into spatio-temporal patterns, and the first two EOF modes were analyzed. According to the first leading EOF mode (48.5%), the temporal variability (Principal Components, PC1) was highly positively correlated with annual series of PDSI (r=+0.99). The variance decomposition method was further applied to explain the inter-decadal temporal and spatial variations of drought relative to the total variation. We find that 90% of total variance was explained by time variance, and both total and time variance dramatically decreased from 1982 to 2013. The total variance was consistent with extreme climate events at the inter-decadal scale (r=0.71, p<0.01). Comparing the influence of climate change on the annual drought in two different long-term periods characterized by dramatic global warming (P1: 1961–1989 and P2: 1990–2013), we find that temperature sensitivity in the P2 was three times more than that in the P1.