Decrease In Evapotranspiration Research Articles

Surface‐driven amplification of Madden–Julian oscillation circulation anomalies across East Africa and its influence on the Turkana jet

AbstractIn semi‐arid environments, rainfall‐driven soil moisture fluctuations exert a strong influence on surface turbulent fluxes. Intraseasonal rainfall variability can therefore impact low‐level atmospheric temperatures and influence regional circulations. Using satellite observations and an atmospheric reanalysis, we investigate whether rainfall variability induced by the Madden–Julian oscillation (MJO) triggers land–atmosphere feedbacks across East Africa.We identify that surface fluxes during the East African wet seasons (March–May and October–December) are sensitive to MJO‐induced precipitation variations across low‐lying regions of South Sudan and highland regions of Uganda and southwest Kenya. For example, during MJO phases 6 to 8, when rainfall is suppressed, surface temperatures and sensible heat fluxes increase, whilst evapotranspiration decreases. Spatial variations in the surface flux response to rainfall variability feed back onto the atmosphere through amplifying MJO‐associated pressure anomalies. During dry MJO events for instance, surface warming across the exit region of the Turkana channel increases the low‐tropospheric along‐channel pressure gradient and intensifies the Turkana jet. We conclude that average surface‐driven temperature fluctuations during a single day are responsible for approximately 12% of MJO‐associated variability of the Turkana jet speed. However, we expect that the accumulation of heat over multiple days to the west of the East African Highlands further amplifies anomalies in the pressure gradient and jet intensity. Modelling experiments are required to quantify the accumulated impact of the surface forcing. Surface‐driven Turkana jet variations influence the East African moisture budget and affect the intensity and inland propagation of coastal convection. Not only is this the first study to investigate the importance of intraseasonal land–atmosphere feedbacks across East Africa, but it is also the first to show that Turkana jet characteristics are partly driven by surface conditions. This work motivates an investigation into whether subseasonal forecast models fully harness the predictability from surface‐induced jet variations.

Estimating ecosystem evaporation and transpiration using a soil moisture coupled two-source energy balance model across FLUXNET sites

The two-source energy balance model coupled with soil moisture (TSEB-SM) was evaluated against observations from a global set of 57 eddy covariance (EC) sites, part of the FLUXNET2015 dataset. In addition, modeled soil evaporation (E) and transpiration (T) were compared with the values obtained from the Transpiration Estimation Algorithm (TEA) and underlying water use efficiency (uWUE) approaches. The TSEB-SM model framework using near-surface soil moisture improved the agreement to EC-observed sensible and latent heat fluxes, reducing mean absolute percentage error (MAPE) by about 30% and root mean square error (RMSE) by about 44 W/m2 across all sites. The results show that the advantage of the TSEB-SM model, with respect to the original TSEB, becomes more evident as the ratio of actual to potential evapotranspiration (AET/PET) decreases. The E and T produced by TSEB-SM has better correlation with the results of uWUE partitioning than TSEB, especially under low soil water content condition. Likewise, TSEB-SM is superior to TSEB in simulating T when compared with sap flow measurements derived from the SAPFLUXNET database. These results imply that the development and application of TSEB-SM has made significant advances in modeling surface water fluxes, even though uncertainties remain. The approach used in TSEB-SM, driving the model with an extensive remotely sensed parameter set, gives valuable information on water use and provides an alternative to Global Climate Models where complex interactions of ecosystems are parametrized. Thus, TSEB-SM provides a unique insight into the flow of energy and the role of surface fluxes in the global water cycle.

Estimation and Spatiotemporal Evolution Analysis of Actual Evapotranspiration in Turpan and Hami Cities Based on Multi-Source Data

The accurate inversion of actual evapotranspiration (ETa) at a regional scale is crucial for understanding water circulation, climate change, and drought monitoring. In this study, we produced a 1 km monthly ETa dataset for Turpan and Hami, two typical arid cities in northwest China, using multi-source remote sensing data, reanalysis information, and the ETMonitor model from 1980 to 2021. We analyzed the spatiotemporal variation of ETa using various statistical approaches and discussed the impact of climate and land use and cover changes (LUCC) on ETa. The results show the following: (1) the estimation results correlate well with ETa products on monthly scales (coefficient of determination (R2) > 0.85, root mean square error (RMSE) < 15 mm/month) with high reliability. (2) The ETa values were spatially distributed similarly to precipitation and LUCC, with the multi-year (1980–2021) average of 66.31 mm and a slightly fluctuating downward trend (−0.19 mm/a). (3) During the 42-year period, 63.16% of the study area exhibited an insignificant decrease in ETa, while 86.85% experienced pronounced fluctuations (coefficient of variation (CV) > 0.20), and 78.83% will show an upward trend in the future. (4) ETa was significantly positively correlated with precipitation (94.17%) and insignificantly positively correlated with temperature (55.81%). The impact of human activities showed an insignificant decreasing trend (85.41%). Additionally, the intensity of ETa varied considerably among land types, with the largest for cropland (424.12 mm/a). The results of the study have implications for promoting the rational allocation of regional water resources and improving water use efficiency in arid zones.

Different hydrological controls causing variable rates of Holocene peat growth in a lowland valley system, north-eastern Netherlands; implications for valley peatland restoration

The Drentsche Aa valley system in the glacial sandy landscape of the north-eastern Netherlands, is one of the many regional drainage systems in the north-western to central European Lowlands. Following deep incision in the Weichselian, ca 7 m of eutrophic peat has accumulated in the lower to middle reaches of the valley system in the Holocene, completely filling the Weichselian incision. We reconstructed the rate of water-level rise controlling peat growth at three locations in the valley system (representing the upper, middle and lower reaches), using 14C peat dates from compaction-free sampling sites on the sloping valley margin where the peat directly overlies the sandy Pleistocene subsurface. The 14C dates enabled the construction of curves showing the water-level evolution at each location. Our results show variable rates of Holocene peat growth in the valley system in response to different drivers of hydrological change: a strong increase in annual precipitation (onset Holocene), a decrease in evapotranspiration (10,000–8000 cal. years BP) and relative sea-level rise (after ~4500 cal. years BP). Because the identified hydrological controls on peat growth are regional, they probably ruled Holocene peat growth in many peat-filled valley systems in the north-western to central European Lowlands. Currently, there is growing attention for these valley systems in the context of European nature restoration efforts and climate change adaptation and mitigation measures. The present study underscores that large-scale hydrological measures outside the valley system are needed for restoration of degraded valley peatlands.

Impacts of Ongoing Land-Use Change on Watershed Hydrology and Crop Production Using an Improved SWAT Model

The southern Ogallala Aquifer continues to deplete due to decades of irrigation with minimal recharge. Recently enacted regulations limiting groundwater withdrawals and the potential for farm profitability with cotton production systems indicate driving forces for increased cotton production acreage in the Northern High Plains of Texas (NHPT). This study focused on evaluating the land-use change from corn or winter wheat to cotton under irrigation and dryland conditions in the Palo Duro watershed (PDW) in the NHPT using an improved Soil and Water Assessment Tool (SWAT) model. Land-use change from irrigated corn to irrigated cotton led to reductions in average (2000–2014) annual irrigation, actual evapotranspiration (ETa), and surface runoff by 21%, 7%, and 63%, respectively. Nevertheless, the replacement of irrigated wheat with irrigated cotton caused irrigation and ETa to increase by 46% and 18%, respectively. Land-use conversion from dryland wheat to dryland cotton showed 0.1% and 15% decreases in ETa and surface runoff, respectively. More than 40% reductions in simulated cotton yields were found when the cotton planting area was moving northward to the cooler NHPT. The ongoing change in land use provided an option to lengthen the water availability of the southern Ogallala Aquifer for irrigation.

Faster evapotranspiration recovery compared to canopy development post clearcutting in a floodplain forest

Actual evapotranspiration (ETa) is a key component of the water balance, and its accurate quantification of spatiotemporal variation is essential to improve the understanding of soil–plant-atmosphere-hydrosphere interactions. While in situ point measurements allow for the determination of the ETa of a particular ecosystem or land cover type, remote sensing methods make it possible to divide and evaluate the rate of ETa of different ecosystems in the landscape and would allow better management of the water resource system, especially if those are partly or permanently limited. The goal of this paper was to analyze the impact of clearcutting during standard forest management practices in floodplain forests and its effect on the water regime of the area. We selected the Lanžhot floodplain forest area (48.681°N 16.950°E, 155 m a.s.l.) that represents a biologically and hydrologically unique area of remnant floodplain forest within the upper Danube River basin. Since clearcutting represents a drastic intervention into the ecosystem including changes in canopy structure and local microclimate, we hypothesized that the impact of the clearcut on the overall water balance is long-term in the order of decades as a result consequence of logging of the mature forest and changes in local microclimatic conditions in disturbed areas. To analyze the impacts of clearcutting on ETa, we applied the METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) remote sensing model. METRIC was validated in the Central European climatic conditions using two ground eddy covariance measurements systems over grassland and floodplain forest. The evaluated model METRIC was then applied to quantify ETa in three areas of interest in the floodplain forest, where in 2015–2021, mature vegetation was targeted for removal, modification of the soil surface, and subsequent planting of a new generation of English oak trees (Quercus robur L.). Immediately after the removal of vegetation cover, METRIC detected an annual decrease in ETa by 35–40%, while leaf area index (LAI) decreased by 70–80%. This was followed by a quick recovery of the ETa/ETo (where ETo represents FAO-56 reference evapotranspiration), reaching similar values as uncut surrounding vegetation during the third year, while LAI recovery was detected in the fifth year after the removal of vegetation cover. The rapid recovery of the ETa/ETo rejected the initial hypothesis, and studies showed that the newly formed stand replaced the ETa/ETo rate of the mature stand in the floodplain forest conditions of Central Europe in the fourth year, suggesting that the impacts of clearcutting on the hydrology may be temporally relatively limited.

Changes In Land Use/ Cover And Water Balance Components During 1964–2010 Period In The Mono River Basin, Togo-Benin

The Intergovernmental Panel on Climate Change has predicted that sub-tropical regions are more vulnerable to climate change’s negative effects (CC). Additionally, to CC, land use and land cover (LULC) changes and dam construction, often neglected, play an important role in the spatial and temporal distribution of water balance components (WBC) for agricultural production and socio-ecological equilibrium. This study aimed to analyze and compare the changes in LULC and WBC for the period before Nangbéto dam construction (1964–1986) and the period after its construction (1988–2010) in the Mono River Basin (MRB). To this end, the study used mainly WBC extracted from the validated Soil and Water Assessment Tool and LULC data of 1975–2000 in the MRB to explore their temporal distributions and the link in their changes. The results showed that mean actual monthly evapotranspiration, percolation, water yield, surface runoff, groundwater, and lateral flow represent 51%, 17.5%, 15.9%, 9.4%; 5.7% and 0.4%, respectively, of total water balance between 1964 and 1986. The same components represented 51%, 9.1%, 20.4%, 6.3%, 10.6% and 2.6%, respectively, between 1988 and 2010. The contribution of these WBC in the mean-annual (1964–1986) period was for actual evapotranspiration (31.3%), water yield (25.9%), percolation (17.7%), groundwater (14.71%), surface runoff (9.94%) and lateral flow (0.40%). Meanwhile, between 1988 and 2010, the contribution of actual evapotranspiration, water yield, percolation, groundwater, surface runoff and lateral flow is 49.8%,19.9%, 11.2%, 10.3%, 6.1%, and 2.5%, respectively. The results showed that the peaks of the actual evapotranspiration, surface runoff, percolation and water yield appeared in September, corresponding to a month after the maximum rainfall in August. However, our more detailed analysis showed that a significant decrease in forest and savanna and an increase in croplands led to a decrease in actual evapotranspiration and lateral flow over the second simulation period compared to the first period of simulation over the MRB scale. These findings showed that sustainable management and conservation of natural vegetation are crucial for integrated water resource management and conservation in MRB.

Wildfire Burn Severity Affects Postfire Shifts in Evapotranspiration in Subalpine Forests

Highlights After wildfire, actual evapotranspiration (ETa) in four subalpine areas decreased proportionally to burn severity. High-severity burn areas maintained the highest ETa before fire and the lowest ETa after fire. After fire, ETa decreased more in areas that had higher prefire ETa. ETa was a useful system-level measure of susceptibility to fire and impact after fire. Abstract. The ecohydrologic response to fire is complex, with devastating consequences for source-water hydrology. Postfire canopy structure, leaf area, infiltration, and soil-water storage all may act to reduce evapotranspiration (ET), a key hydrologic variable and indicator of ecohydrologic function. This study explored the use of 30-m resolution Landsat-based SSEBop-model estimates of actual ET (ETa) to assess the effects of fire in the Upper Rio Grande Basin (2002 Million Fire, CO; 1996 Hondo Fire, NM; 2002 Montoya Fire, NM; 2000 Cerro Grande Fire, NM). SSEBop ETa data from 1985-2019 were analyzed to better understand postfire response and recovery in several sub-alpine burned areas. Results show step reductions in ETa after fire across all burn severities in all four fire areas. Prior to the fire, ETa was generally higher in high-severity burn areas, indicative of higher fuel loads, although high variability indicated the influence of additional factors. All areas had a greater response (decreased ETa) to fire in high-severity areas and a lesser response as burn severity decreased. The decrease in ETa after high-severity fire ranged from 42% to 63%, compared to the decrease after low-severity fire, which ranged from 24% to 44%. None of the four burn areas demonstrated postfire ETa recovery after 17 to 23 years. This study demonstrates the clear utility for remote-sensing ETa estimates as a system-level measure of susceptibility to fire, impact of fire, and, potentially, recovery after fire. However, additional research is needed to account for the covariate effects of other fuel, topographic, weather, and climate factors. Keywords: Ecohydrology, Postfire recovery, Remote sensing, Upper Rio Grande Basin.

Drip irrigation improves spring wheat water productivity by reducing leaf area while increasing yield

To mitigate the climate change-induced water shortage and realize the sustainable development of agriculture, drip irrigation, a more efficient water-saving irrigation method, has been intensively implemented in most arid agricultural regions in the world. However, compared to traditional border irrigation, how drip irrigation affects the biophysical conditions in the cropland and how crops physiologically respond to changes in biophysical conditions in terms of water, heat and carbon exchange remain largely unknown. In view of the above situation, to reveal the mechanism of drip irrigation in improving spring wheat water productivity, paired field experiments based on drip irrigation and border irrigation were conducted to extensively monitor water and heat fluxes at a typical spring wheat field (Triticum aestivum L.) in Northwest China during 2017–2020. The results showed that drip irrigation improved yield by 10.3 % and crop water productivity (i.e., yield-to-evapotranspiration-ratio) by 15.6 %, but reduced LAI by 16.9 % in contrast with border irrigation. Under drip irrigation, the lateral development of spring wheat roots was promoted by higher soil temperature combined with frequent dry-wet alternation in the shallow soil layer (0–20 cm), which was the basis for efficient absorption of water and fertilizer, as well as efficient formation of photosynthate. Meanwhile, drip irrigation increased net radiation and decreased latent heat flux by inhibiting leaf growth, thereby increased sensible heat, causing a higher soil temperature (+1.10 ℃) and canopy temperature (+1.11 ℃). Further analysis proved that soil temperature was the key factor affecting yield formation. Based on the above conditions, the decrease in leaf distribution coefficient (−0.030) led to the decrease in evapotranspiration (−5.7 %) and the increase in ear distribution coefficient (+0.029). Therefore, drip irrigation emphasized the role of soil moisture in the soil-plant-atmosphere continuum, enhanced crop activity by increasing field temperature, especially soil temperature, and finally improved yield and water productivity via carbon reallocation. The study revealed the mechanism of drip irrigation for improving spring wheat yield, and would contribute to improving Earth system models in representing agricultural cropland ecosystems with drip irrigation and predicting the subsequent biophysical and biogeochemical feedbacks to climate change.

Sensitivity of evapotranspiration and seepage to elevated atmospheric [formula omitted] from lysimeter experiments in a montane grassland

The response of vegetation to elevated atmospheric carbon dioxide (eCO2) has opposing effects on terrestrial water fluxes, especially evapotranspiration. In particular, CO2 fertilization may enhance plant growth, therefore increasing canopy transpiration, while a partial stomatal closure decreases leaf transpiration. In this study, the effects of eCO2 on water fluxes at a managed montane grassland were monitored using two high precision weighable lysimeters exposed to ambient and elevated (+300 ppm relative to ambient conditions) CO2 concentrations. During the growing season, eCO2 led to a general decrease in evapotranspiration and an increase in seepage. It was shown that eCO2 influences evapotranspiration primarily through the change in stomatal resistance, as no effect of eCO2 on the leaf area index was confirmed. A CO2-dependent Penman–Monteith equation and actual evapotranspiration data from the lysimeters made it possible to estimate the effect of eCO2 on stomatal resistance. eCO2 was found to increase stomatal resistance by 50% relative to ambient conditions. A HYDRUS-1D model allowed a temporal extension of the experimental findings to the period of 1990–2021 and revealed high variability in the relative change in annual seepage under eCO2. The modeling exercise demonstrated that the effect of eCO2 can be easily implemented in the Penman–Monteith equation, and if neglected, leads to overestimation of transpiration and underestimation of seepage, especially in the first post-drought seepage events. Our findings show that eCO2 positively affects the water balance in montane grasslands, thus eCO2 might be an important factor in mitigating the effects of warming and droughts in the future. We propose that the vegetation response to eCO2, in particular the effect on stomatal resistance, should be taken into account when assessing the effects of climate change on grassland water fluxes. This may also have large implications when studying the impact of climate change at a watershed scale.

Increasing land productivity with agriphotovoltaics: Application to an alfalfa field

Agriphotovoltaic systems, consisting of the combination of crops and photovoltaic panels (PVPs) on the same area, have recently emerged as an opportunity to solve the competition for land use between food and energy production. Various crops, pedoclimatic contexts and structures and both fixed and mobile panels have been studied. Over a period of two years, this research has been investigating an agriphotovoltaic (APV) system with mobile panels along two axes of rotation. The studied crop is alfalfa, a grassland species that has received little attention under these conditions. In our experimental set-up, the alfalfa biomass increased by an average of 10 % over the two years of the experiment in the shade of the APV plant (between 29 % − 44 %) in comparison to full sunlight (835 g.m−2.year−1), but in a different way depending on the climatic year. The nutritional qualities were preserved while the canopy's morphology was adapted through an increase in the length of the stems and the surface area of the leaflets. Photovoltaic production was reduced by 15 % due to the optimised tracking for plant growth. This combined production allowed an increase in total productivity per unit area of 51 % (LER: 1.51). The positive agronomic results are explained by a decrease in evapotranspiration caused by the panels in a context where the crop is highly sensitive to water deficit with thin soil. To reach a more general conclusion on synergy, these results need to be completed over several years and compared with other studies in different soil and climatic contexts, as well as with modelling studies.

Climatic implication of stalagmite δ13C in the middle reaches of the Yangtze River since the Last Glacial Maximum and coupling with δ18O

The relationship between monsoon circulation and regional hydrology in the Yangtze River Basin since the Last Glacial Maximum (LGM) remains unclear. In this study, we present speleothem (LS46) δ18O and δ13C records over the past 23.5 kyr from the Luoshui Cave in Central China. Stalagmite LS46 δ13C displayed a good similarity with variations in δDwax-derived monsoon precipitation from Lake TengchongQinghai (TCQH) and the extreme precipitation events identified by the IRMsoft-flux from Heshang Cave, thus indicating that speleothem calcite δ13C reflects the changes in regional hydrology. The ensemble empirical mode decomposition (EEMD) and wavelet spectrum analyses revealed that the regional hydrology was paced by ∼2000-year periodicity during the LGM and last deglaciation and ∼ 1000-year periodicity during the Holocene, respectively. Our results further indicated that the El Niño-Southern Oscillation (ENSO) plays an important role in regulating changes in the frequency and magnitude of regional hydrology in the Yangtze River Basin under different climatic conditions. Moreover, our results demonstrated that δ18O and δ13C were coupled on multiple timescales, thus potentially indicating that local hydrological variations in the middle reaches of the Yangtze River are regulated by large-scale monsoonal circulation. However, we also found that the δ18O and δ13C profiles decoupled during the last deglaciation, likely due to a decrease in evapotranspiration in combination with a decrease in monsoon intensity and temperature during this period. Consequently, the regional hydrological conditions did not experience any dramatic changes.

Effects of mulching on water saving, yield increase and emission reduction for maize in China

Mulching, an agricultural management measure widely used in arid and semi-arid regions of China, can effectively improve the hydrothermal environment of farmland and increase crop yield and crop water productivity (WPc). However, previous studies on the effects of mulching on water saving, yield increase and emission reduction of maize have provided inconsistent results. Therefore, a meta-analysis was used in this study to (1) evaluate the effect of mulching types [plastic film (PM), straw (SM) and degradable film (DM)] on maize yield, evapotranspiration, WPc and greenhouse gas emissions; and (2) determine the effects of mulching measures on water saving, yield increase and emission reduction in maize farmland under different climatic conditions. Compared with the no-mulching control, mulching significantly raised maize yield, WPc and carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The PM, SM and DM increased maize yield by 27.31 %, 6.98 % and 16.55 % compared with no-mulching, respectively, and correspondingly WPc by 34.08 %, 11.48 % and 24.20 %. The PM and SM significantly increased CO2 emissions by 39.91 % and 16.43 %, respectively, and N2O emissions by 51.1 % and 30.12 %, but had no significant effect on methane absorption. For maize planting, in areas with altitudes < 500 and > 1000 m, average annual rainfall < 1000 mm, average annual air temperature of 5–15 °C and average annual evaporation < 1500 mm, a combination of PM and ridge–furrow planting can achieve the best effect of increasing production and saving water. In areas with an altitude of 1000–1500 m and average annual evaporation of 1500–2000 mm, the DM had the greatest effect of improving yield (by 16.17 %) and saving water, with a decrease in evapotranspiration of 8.82 % and an increase in WPc of 24.71 %. The local level of mechanization and labor costs should be considered when choosing a maize mulching pattern.

The Spatiotemporal Change of Xiao Qaidam Lake from 1990 to 2020 and Its Potential Hazards

In the climatic context of warming and humidification in Northwest China, most lakes in Qinghai Province experienced a rising water level and expanding area, inundating grassland and infrastructure around lakes, and even extreme events such as lake outburst floods. Based on Landsat TM/ETM+/OLI and GF PMS images, lake water level data, SRTM digital elevation model (DEM), GlobeLand30 and meteorological data used in this study, we analyzed the area change of Xiao Qaidam Lake in Qaidam Basin with its causes, factors and potential hazards. The results show that the area of Xiao Qaidam Lake increased by 60.42 km2 (85.43%) from 1990 to 2020, which can be roughly divided into three stages: fluctuation decline in 1990–2001 (−1.89 km2/a); relatively stable in 2002–2014; and rapid expansion in 2015–2020 (8.54 km2/a). In 2020, the water level and water volume of Xiao Qaidam Lake increased by 3.62 m and 0.39 km3, respectively, compared with 2015, resulting in the inundation of an area of 54.55 km2 of grassland around the lake and a direct threat to the Liuge and Dexiao Expressways. Both the increase in annual precipitation (12.63 mm/10a) and the decrease in potential evapotranspiration (−13.38 mm/10a) since 1990 are the main reasons for the rapid expansion of Xiao Qaidam Lake, and the increasing trend of climate warming and humidification will lead to the continuous expansion of Xiao Qaidam Lake in the next decades. According to the water volume growth rate from 2015 to 2020, it is predicted that by 2024 the area and water level of Xiao Qaidam Lake will reach 154 km2 and 3180 m, respectively, and part of Liuge and Dexiao Expressways will be submerged. Therefore, it is urgent to strengthen the monitoring of Xiao Qaidam Lake and formulate corresponding disaster prevention and reduction measures.

The Coupling of Soil Water and Leaf Phenology Observed by Satellite During Australian Bushfires in 2019–2020

AbstractWater and energy fluxes at the interface between the surface of the earth and the atmosphere depend strongly on soil moisture. Surface soil moisture (SSM) participates in natural phenomena such as evaporation, infiltration and runoff. From 2019 to 2020, bushfires in Australia caused changes in the runoff of surface water, the transpiration of vegetation, and evapotranspiration of the soil, subsequently affecting the soil water cycle. However, the dynamics of surface soil water content during large‐scale bushfires are still not completely understood. Here, we report on patterns of seasonal variation in SSM and vegetation leaf phenology in Australia, identified using L‐band radiometric measurements of soil moisture taken by the soil moisture and ocean salinity mission from 2011 to 2020. This study reveals a decrease in the leaf area index in affected regions of New South Wales, Victoria, Queensland, Western Australia, Australian Capital Territory, Northern Territory, and Tasmania. The observed seasonal variations in SSM are highly synchronous with those of leaf phenology in northern and northeastern Australia. However, the development of the leaf area lags behind that of SSM for up to 90 days in the southeastern subtropical woodlands. The time lag between leaf area development and SSM in the southwest is about 60 days. Bushfires can lead to the decrease of evapotranspiration hence shortening the time lag between SSM and leaf phenology. Our results offer insights into the variations in SSM during bushfires, the relationship between SSM and leaf phenology in Australia, and lay a foundation for improving models of ecological hydrology during bushfires.

Evaluating changes in catchment‐scale evapotranspiration after 50% strip‐thinning in a headwater catchment

AbstractWe examined changes in catchment‐scale annual and seasonal evapotranspiration after 50% strip thinning, using runoff data from headwater catchments. The short‐term water balance (STWB) method between periods from 8 to 100 days was applied to the treated (KT) and control (KC) catchments. The estimated evapotranspiration during the pre‐ and post‐thinning periods were 840 and 910 and 780 and 860 mm/year in the catchments KT and KC, respectively. According to a paired catchment analysis of estimated evapotranspiration, monthly evapotranspiration increased from 3 to 20 mm from June to December, while it decreased from 7 to 31 mm from January to May. The estimated annual and monthly evapotranspiration was compatible with the values monitored in the plot‐scale interception, canopy transpiration, and ground surface evapotranspiration. Our findings showed that the decreases in evapotranspiration due to 50% thinning were similar or different in different methods of measurement when compared with thinning in the other catchments around the world. The STWB model can evaluate the effects of timber harvesting on changes in evapotranspiration (ET), including the reproduction of seasonal patterns of ET.

Avaliação das Mudanças Climáticas Usando o índice de Humidade da Classificação Climática Thornthwaite no Bioma Pantanal

Abstract Thornthwaite climate classification indices are essential to interpret climate types in the state of the pantanal biome (Mato Grosso do Sul), simplifying calculation process and interpretation of climatological water balance by farmers. However, there are few studies found in the literature that characterize the climate of pantanel biome in different climatic scenarios. We seek to assess climate change using humidity index of Thornthwaite climate classification in pantanal biome. We used historical series of climate data from all 79 municipalities of Mato Grosso do Sul between 1987 and 2017, which were divided into microregions. Air temperature and precipitation were collected on a daily scale. Precipitation and potential evapotranspiration data allowed calculating water balance by the Thornthwaite and Mather method. We characterized all locations as wet and dry using aridity indices proposed by Thornthwaite. The global climate model used was BCC-CSM 1.1 developed at the Beijing Climate Center (BCC) with a resolution of 125 x 125 km. We used the scenarios RCP-2.6, RCP-4, RCP-6 and RCP-8.5 for analyzing 21st century projections (2041-2060 and 2061-2080 periods). Maps were generated from climate indices of Mato Grosso do Sul using kriging interpolation method with spherical model, one neighbor, and 0.25° resolution. The microregions showed different patterns regarding water balance components and humidity index. Humidity index had a mean of 15.94. The prevailing climate in the state of Mato Grosso do Sul is C2 (moist subhumid). The state of Mato Grosso do Sul has two well-defined periods during the year: a dry and a rainy period. Three climate types predominate in Mato Grosso do Sul and, according to the Thornthwaite classification, are B1 (humid), C2 (moist subhumid), and C1 (dry subhumid). Water characterization in Mato Grosso do Sul showed 234.78 mm year−1 of water surplus, 80.8 mm year−1 of water deficit, and 1,114.8 mm year−1 of potential evapotranspiration. Water deficit and potential evapotranspiration decrease as latitude increases. The climatic projections show, in all scenarios, reduce the area classified as umida in the state (B1, B2 and B3), besides adding the dry subhumid class (C1). The Scenario RCP 8.5 in 2061 - 2080 is the most worrisome situation of all, because the state can undergo major changes, especially in the pantanal biome region.

Understanding land use/land cover and climate change impacts on hydrological components of Usri watershed, India

Land use/cover (LULC) and climate are significant environmental factors that influence watershed hydrology across the globe. The present study attempts to understand the consequences of existing changing patterns of climate and LULC on the hydrology of the Usri watershed. Different water balance components were simulated using a semi-distributed Soil and Water Assessment Tool (SWAT) model. Sixteen scenarios were generated using combinations of four periods of climatic data (1974–84; 1985–1995; 1996–2006 and 2007–2016) and four sets of land use maps (1976; 1989; 2000 and 2014). The SWAT model performed well for monthly stream flows during calibration and validation. The study finds that the individual impact of LULC change contributes to increase in the streamflow and decrease in evapotranspiration (ET) primarily due to increase in urbanization and decrease in water bodies, forest cover and barren land of Usri watershed. The combined impact of climatic variations and land use change reveals complex interactions. The study provides insight into hydrological response to variations in climate and land use changes in Usri watershed in recent decades. The results of this study can be beneficial to the authorities, decision-makers, water resource engineers and planners for the best water resource management approaches in the perspective of climate change and LULC transformation of similar ecological regions as that of Usri.

An investigation of reference evapotranspiration trends for crop water requirement estimation in Rajasthan

Trends in reference evapotranspiration (ETo) estimated using Penman-Monteith equation were analysed over arid, semi-arid and humid regions of northwest (NW) India during 1985–2018. The MannKendall is used to determine significance of trends. Theil-Sen’s estimator and least square linear fitting methods are adopted to find slopes of the trend lines. The results indicated a significant decrease in ETo on annual basis for most of the locations and NW India as a whole. However, the trend was not statisticallysignificant for seasonal ETo. The significant decrease in solar radiation and wind speed nullified the impact of increased temperature and resulted in slight decrease in ETo over arid and semi-arid regions of NW India which could probably be attributed to the increased dust hazy conditions prevailing. In NW India, water is a limiting resource the decrease in ETo may help researchers in decision makers to develop water assets and utilize the irrigation systems more effectively. There was also an increasing trend in production of major crops in the study region. Further, in near future, if this decreasing ETo trend were to remain, it would help in intensification of cropping system with the existing water resource.

Waxing and waning slacks: The changing ecohydrology of interdunal wetlands/slacks in a Lake Michigan coastal dune complex during rising Lake Michigan-Huron levels

Since 2016 we have studied the largest interdunal wetlands/slack lying within a deflated parabolic dune east of Lake Michigan. Geologic cross-sections show ∼ 15 m of sand and gravel beneath the dunes, creating an aquifer hydraulically connecting Lake Michigan-Huron (MH) with the water table/shallow groundwater influencing the slack. Lake Michigan-Huron (MH) water levels have risen ∼ 1 m from 2016 to 2020, increasing water levels within and around the slack ∼ 1 m. Color-infrared images and vegetation quadrat sampling show water appearing, then significantly expanding with the main slack and upland/dune vegetation transitioning to wetland vegetation in response to this rise. Monitoring well data show slack water levels rise in spring as Lake MH rises. Levels drop as the growing season begins while Lake MH continues to rise through summer. Short-term slack water level increases occur due to local rain events, but significant water level declines follow due to evapotranspiration. Slack water levels begin to rise again in late summer and into fall as the end of the growing season arrives, evapotranspiration decreases, and heavier, more frequent rain events occur. Together, these factors push slack water levels to their highest point of the year while Lake MH levels are decreasing. In late fall–winter, slack water levels drop in concert with Lake MH levels. Climate change effects, increased transpiration from higher temperatures, summer drought, and greater variability in lake level fluctuations, may make it more difficult to maintain wet growing conditions for hydrophytic vegetation. Hence, climate change poses risks to the existence of this imperiled ecosystem.