Variations In Soil Water Storage Research Articles

Intercomparison of micrometeorological variables, surface energy fluxes, and evapotranspiration in different landscapes of the Brazilian semi-arid region

The comparison of energy exchanges between different landscapes is very valuable for understanding the consequences of deforestation and land use change on the climate. In this study, we analyzed micrometeorological variables, energy fluxes, and actual evapotranspiration over four landscapes of the Brazilian semi-arid region (preserved Caatinga – CAA, regenerating Caatinga – REGE, cactus landscape – CAM and deforested landscape – DEFA). Micrometeorological measurements (air temperature and relative humidity, vapor pressure deficit), net radiation (RN), latent heat (LE), sensible (H) and soil heat (G) fluxes, actual evapotranspiration (ET), and soil water storage variation (ΔS) were obtained in landscapes from October 2018 to September 2020. LE and H were calculated based on the Bowen ratio method. Significant differences were noted between micrometeorological variables (temperature and relative humidity, and vapor pressure deficit) and energy flux among the four landscapes. The four surfaces exhibited, on average, lower LE values when compared to H. At CAA landscape, 35% of the RN was used for LE, 64% for H, and 1% for G, versus 33% for LE, 65% for H, and 2% for G at REGE; 33% RN for LE, 65% for H and 2% for G at CAM, and 40% for LE, 59% for H and 1% for G at DEFA. The evapotranspiration for regenerating Caatinga (1.62 mm day−1), cactus (1.59 mm day−1), and deforested area (1.90 mm day−1) were higher than the preserved Caatinga (1.40 mm day−1). However, seasonal variations of the ET were more associated with fluctuations in RN, rainfall, and ΔS than with the type of land use. It is concluded that the removal of Caatinga by landscapes such as regenerating Caatinga, cactus plantations, and deforested area significantly modifies micrometeorological variables, energy fluxes, and the evapotranspiration, but their seasonality depends on the regime availability of water and energy.

Afforestation reduced the deep profile soil water sustainability on the semiarid Loess Plateau

Insight into the response of deep soil moisture (SM) to land cover change is crucial for the sustainable management of regional water resources and ecosystems. However, the deep soil water budget and resilience after revegetation are not clear. In this study, seven typical land-cover patterns (artificial arbor, shrub, economic tree, pasture, abandon grassland, and natural grassland) were selected in four different study sites on the Loess Plateau of China. From May 2019 to December 2020, SM was monitored daily at ten depths along a 10 m profile in situ to assess the effect of revegetation on the vertical distribution, availability, and sustainability of soil water. The results indicated that the minimum SM moved to the deeper depth in the planted forest, while the maximum SM gradually moved to a shallower and deeper depth after the conversion of cropland to forestland and grassland, respectively. The difference in soil water use strategies under different revegetation types generated the opposite effect on deep SM availability, resilience, and sustainability. Conversion of cropland to grassland realized the deep soil available water (SAW) increment by 53.3% over the entire measurement period. Besides, the grassland promoting the deep soil water resilience (SWR) and soil water storage variation (ΔSWS) enhanced by 41.6% and 708.7% below 2 m depth, respectively. Whereas, compared to cropland, afforestation decreased the SAW, SWR, and ΔSWS by 17.2%, 10.5%, and 570.7% below 2 m depth, respectively. Furthermore, the deep SWR and ΔSWS were basically negative in the forestland, resulting in an unbalanced deep soil water budget within the year. Despite the significant disadvantages of sustaining the availability and water budget of deep soil water in artificial vegetation, constructing a reasonable land cover and vegetation structure could achieve the soil–water environment balance and the sustainable utilization of ecosystem water resources in the semiarid Chinese Loess Plateau (CLP). The findings of this study provide valuable references and guidance for sustainable vegetation conservation and water resource management and provide design and optimization solutions for vegetation restoration in similar areas of arid and semiarid regions around the world.

Use of Soil Infiltration Capacity and Stream Flow Velocity to Estimate Physical Flood Vulnerability under Land-Use Change Scenarios

Land-use changes produce variations in upper soil hydraulic properties and alter the hydrological response and hydraulic behavior of streams. Thus, the combined effect of variations in soil properties and current hydraulics interacts with the exposure of structures exposed and their degree of physical vulnerability. This study aims to evaluate the effect of land-use evolution from 1976 to 2017 on the physical vulnerability of structures exposed to floods in the Combeima cathment, Colombia, proposing two novel approaches: (i) based on soil infiltration capacity variation (CN) in the basin and changes in stream flow velocity (v), (ii) through soil water storage variation in the root zone (Hu). Hydrological and hydraulic modeling and the implementation of four physical vulnerability assessment methods were performed using GIS analysis. Findings indicate that simplifying physical vulnerability estimations through CN, Hu, and v variations in catchments and at cross-section resolutions is possible, allowing a detailed analysis of the land-use change effect on the vulnerability of structures. The scaling behavior of the physical vulnerability of structures was identified when Hu is defined as a scale variable and, similarly, concerning flow velocity in the stream. Therefore, applying the power law could be useful in planning processes with limited information.

Dynamic changes in soil moisture in three typical landscapes of the Heihe River Basin

The water diversion scheme of Heihe River Basin was implemented in 2000. Herein, we investigated the dynamic changes in soil moisture content and analyzed the fundamental reasons supporting the water diversion plan in this typical inland river basin in northwest China. Accordingly, we selected three typical landscape gradients—a mountain water conservation forest belt, an artificial sand-fixing forest belt at the edge of a desert oasis, and a desert riparian forest belt in the upper, middle, and lower reaches of the Heihe River Basin, respectively. In these diverse landscapes, an environmental measuring system was used to continuously monitor the dynamic and differentiation regularity of soil moisture in the 0–160 cm layer for 5 years. The results revealed that 1) the soil moisture content in each landscape increased and varied significantly across seasons. In the upper and middle reaches, the soil moisture content was significantly higher during the growing season than in the non-growing season, whereas the lower reach displayed a converse pattern. 2) The distribution of soil moisture at various depths of soil profiles varied significantly for each landscape. As the soil depth increased, the soil moisture in the upper reach decreased. Although the deep layers (120–160 cm) could store water in the non-growing season, the stored water was consumed during the growing season. The soil moisture content in the mid-reach initially increased, later decreased, and ultimately attained its highest level at 40–60 cm; however, the soil moisture content in the lower reach increased, and reached its highest level at 120–160 cm. 3) In the upper and middle reaches, the coefficient of variation of soil moisture decreased with an increasing soil depth, whereas the lower reach exhibited a converse trend. Similarly, the coefficient of variation of soil water storage were higher during the non-growing season than during the growing season within the upper and middle reaches, whereas an opposite trend was observed in the lower reach. 4) Since the implementation of the Heihe river water diversion plan, the soil moisture content in both the upper and middle reaches have increased but that of the lower reach has fluctuated and declined, especially in the shallow depths during the growing season. The present findings imply that the lower reaches of the Heihe River may require additional water transfers during the growing season.

Spatiotemporal soil water storage variation comparison between newly formed and untreated gully land sites under a land restoration project and associated implications on land management

Soil water storage (SWS) can effectively be used as an important indicator to manage soil water resources in water-limited ecosystems, being strongly linked to land-use and land management changes. The Government of China launched the Gully Land Consolidation (GLC) project in 2011 to reclaim landforms and resolve land scarcity and food shortages in the Chinese Loess Plateau (CLP) without endangering the environment. Corollary effects of this project were alterations to original landscapes and associated hydrological processes. However, temporal dynamics in available soil water of the newly formed land for cultivation purposes remain unclear. Accordingly, this study measured SWS to a 5 m soil depth over a 5-year period at two gully sites, one newly formed under the GLC project (i.e., the experimental site) and the other left untreated (i.e., the control). SWS exhibited similarly weak temporal variation at both gully sites (coefficient of variation [CV] = 6% at the experimental site; CV = 11% at the control site). Although SWS always negatively correlated to mean temperature and wind speed (p < 0.05) with no observable hysteresis, SWS responded to precipitation at both sites with obvious hysteresis (experimental site = two month hysteresis; control site = three months hysteresis). Seasonal SWS characteristics confirmed the lag response to precipitation. Moreover, spatial SWS patterns differed distinctly at both sites. The mean proportion of available SWS to the available water holding capacity was 69% at the experimental site, indicating that stored soil water was available for crop cultivation without the threat of water shortages. Our results provide new insight into spatial and temporal SWS variation in newly formed land engineered by restoration projects. Furthermore, clarifying SWS temporal dynamics and spatial distributions based on long-term monitoring is essential to evaluate, model, and manage water resources in areas affected by anthropic activities.

Validation of the ISAREG model for the irrigation management of the melon crop in the state of Ceará

The research aimed to validate the ISAREG model, introducing it to water management studies in irrigation in the State of Ceará, comparing results of experimental research, with results of simulations, carried out with the use of software, analyzing the following variables: crop evapotranspiration, variation of soil water storage and water flow in the soil. A bibliographic survey was carried out to obtain soil, climate and crop information required by the model to perform the soil water balance. Aiming at the validation of ISAREG, the model was fed with the following data: reference evapotranspiration, precipitation, phenological phases of the crop, effective depth of the root system, water availability factor in the soil, crop coefficient and soil information. Subsequently, the irrigation management option "dates and irrigation depths" was selected, and ISAREG performed the simulation of the soil water balance. The ISAREG demonstrated a detailed soil water balance, being validated in this study, because when its results were compared to the experimental ones, there was similarity in the trends of the variables analyzed, despite the reduced correlation verified regarding the variation of water storage in the soil.

Soil-water deficit in deep soil layers results from the planted forest in a semi-arid sandy land: Implications for sustainable agroforestry water management

Forest planting is a common practice in semi-arid sandy land restoration, but problems may appear associated with forest age like higher soil water consumption that threatens restoration program’s success. This study quantified the distribution and variation of soil water storage in a Pinus sylvestris (P. sylvestris) plantation under various stand ages (20, 30, 40, 50 and 60 years) along 0–1000 cm soil profile in the Mu Us sandy lands (North China). Results indicated that the 20-yr forests mainly consumed the soil water of the 0–200 cm depth soil profile, the 30-yr and 40-yr forests mainly consumed the soil water of the depth of 0–400 cm, whereas the oldest (50–60-yr) pines mainly consumed the soil water located at the deepest soil profile (500–700 cm). Variation of soil water storage (△SWS) was decreased with stand ages, reaching the minimum value in the 30–40-yr stands, and then gradually increased in the 50–60-yr stands. The △SWS was relatively uniform on the 50-yr and 60-yr stands. this pattern was associated with soil desiccation and soil-water depletion. The lower △SWS indicated lower soil water storage which was associated with soil desiccation and soil-water depletion. These findings proved that planted forest gradually aggravated soil water consumption along the increasing forest age, caused a serious soil water deficit in the 200–700 cm depth soil layer, which may be exceeding the water environmental carrying capacity. Therefore, we suggest that forest should be thinned on the periods with the highest △SWS, which would maintain long-term forest sustainability by minimizing soil desiccation for planted forest management in semi-arid sandy lands.

Effect of irrigation and fertilization regimes on grain yield, water and nitrogen productivity of mulching cultivated maize (Zea mays L.) in the Hetao Irrigation District of China

Irrigation and fertilizer management are essential for sustainable development of agriculture in the arid and semiarid regions. In order to obtain high yield production, over irrigation and fertilization are frequently conducted by the farmer which results in a series of environmental problems in particular in the shallow groundwater areas. In this paper, two-year field experiments were conducted to investigate the effect of irrigation and fertilization regimes on grain yield, water and nitrogen productivity of mulching cultivated maize (Zea mays L.) in the Hetao Irrigation District of China. Two irrigation methods, i.e., drip and border irrigation, with different schedules were manipulated in silt loam soil. The border irrigation included two/three different water levels and drip irrigation was triggered by a tensiometer located at a depth of 25 cm with different matric potentials (−15, −25 and −35 kPa). Three different nitrogen fertilization levels (350, 250 and 150 kg ha−1) were applied under drip irrigation controlled by the matric potential of −25 kPa. Soil water storage variation indicated that the active root zone concentrated at a depth of 35−60 cm in the border irrigated plots and 25−45 cm in the drip irrigated plots. Around 16 % of irrigated water (71 out of 450 mm) and 18 % of supplied nitrogen fertilizer (64 out of 350 kg ha−1) were percolated into deeper zone for the farmer’s irrigation and fertilization schedules. Border irrigation water reduced from 450 to 315 mm could decrease the deep percolation without yield reduction. Almost no deep percolation was detected in drip irrigation for three different matric potential controls. The highest yield, water and nitrogen productivity obtained from the drip irrigated plots triggered by matric potential of −15 kPa. Considering yield, water and nitrogen productivity, environmental factors and farmer’s net-profit, drip irrigation at the matric potential of −15 kPa with 250 kg ha−1 nitrogen fertilizer or border irrigation of 315 mm is recommended for mulching cultivated maize in silt loam soil in the Hetao Irrigation District. The nitrogen fertilizer schedule in border irrigation is desirable for optimal application.

Five‐year soil moisture response of typical cultivated grasslands in a semiarid area: Implications for vegetation restoration

AbstractSoil water deficit is one of the important abiotic stresses affecting vegetation restoration. The magnitude and spatiotemporal dynamics of soil water content (SWC) provide basic guidance for optimal vegetation restoration. In a semiarid Chinese area, the changes in the soil water storage (SWS) of five cultivated grasslands and one wasteland were observed, to evaluate the water consumption at different soil depths (0–100 cm), from 2008 to 2012. The plants of the three leguminous species consumed more water in deep soil layers (80–100 cm) and produced more aboveground biomass than the plants of the two gramineous species. The gramineous plants mainly consumed shallow soil water (0 ≤ 30 cm). The soil water deficit in the whole soil profile of Medicago sativa grassland (43–48%) was significantly higher than the deficit of the gramineous grasslands (p &lt; .05). After 5 years of planting, the SWC of Agropyron cristatum grassland (21%) was the highest in the 20‐ to 80‐cm soil layer. The variation of SWS in M. sativa grassland did not significantly differ during this period, although its mean value was 28% lower than the value in A. cristatum grassland (181 mm). At the end of the experiment, leguminous grasslands caused a serious soil water shortage deficit in the 80‐ to 100‐cm soil layers. These results underscore that vegetation type determines the vertical distribution of soil water deficit, particularly in deep layers. To promote long‐term sustainability of water resources, planting A. cristatum may be a good choice for early grassland restoration in arid areas.

Soil water storage variability in a three-dimensional analysis in the root zone of irrigated melon

ABSTRACT A detailed knowledge of the soil water storage variability in the root zone can promote recommendations regarding the ideal positioning of sensors, as well as make the calculation of soil water balance more precise and accurate. This study aimed to assess soil water storage variability in the melon root zone and indicate – based on spatial variation of soil water storage – the regions of highest rootactivity of the melon crop in different development stages. Soil waterstorage was measured using time domain reflectometry (TDR) in 40 monitoring points. The data were daily collected in two periods: (i) immediately before irrigation and (ii) 30 min after irrigation. The soil water storage variation in the melon root zone occurs with greater intensity throughout the time of vegetative growth and the highest values are always observed in the same distances and depths of the soil in all phases of growth. The region indicated as of greatest root activity of the melon crop under drip irrigation is delimited, inrelation to the stem, by the radial distance of 0.36 m and depth of0.3 m, for all development stages.

Season‐based rainfall–runoff modelling using the probability‐distributed model (PDM) for large basins in southeastern Brazil

AbstractSoutheastern Brazil is characterized by seasonal rainfall variability. This can have a great social, economic, and environmental impact due to both excessive and deficient water availability. During 2014 and 2015, the region experienced one of the most severe droughts since 1960. The resulting water crisis has seriously affected water supply to the metropolitan region of São Paulo and hydroelectric power generation throughout the entire country. This research considered the upstream basins of the southeastern Brazilian reservoirs Cantareira (2,279 km2; water supply) and Emborcação (29,076 km2), Três Marias (51,576 km2), Furnas (52,197 km2), and Mascarenhas (71,649 km2; hydropower) for hydrological modelling. It made the first attempt at configuring a season‐based probability‐distributed model (PDM‐CEMADEN) for simulating different hydrological processes during wet and dry seasons. The model successfully reproduced the intra‐annual and interannual variability of the upstream inflows during 1985–2015. The performance of the model was very satisfactory not only during the wet, dry, and transitional seasons separately but also during the whole period. The best performance was obtained for the upstream basin of Furnas, as it had the highest quality daily precipitation and potential evapotranspiration data. The Nash–Sutcliffe efficiency and logarithmic Nash–Sutcliffe efficiency were 0.92 and 0.93 for the calibration period 1984–2001, 0.87 and 0.88 for the validation period 2001–2010, and 0.93 and 0.90 for the validation period 2010–2015, respectively. Results indicated that during the wet season, the upstream basins have a larger capacity and variation of soil water storage, a larger soil water conductivity, and quicker surface water flow than during the dry season. The added complexity of configuring a season‐based PDM‐CEMADEN relative to the traditional model is well justified by its capacity to better reproduce initial conditions for hydrological forecasting and prediction. The PDM‐CEMADEN is a simple, efficient, and easy‐to‐use model, and it will facilitate early decision making and implement adaptation measures relating to disaster prevention for reservoirs with large‐sized upstream basins.

Soil water depletion patterns of artificial forest species and ages on the Loess Plateau (China)

Afforestation as an effective measure to control soil erosion has achieved remarkable effects in northern China. However, large scale of artificial afforestation can increase soil water consumption and induce soil desiccation in arid and semi-arid areas. This study analyzed the variations of soil water storage following the conversion of croplands into forests with different species and stand ages on the Loess Plateau. Three most common artificial forests dominated by Salix matsudana, Populus cathayana, and Sophora japonica with stand ages of 5, 10, and 15 years were investigated to determine the variations in soil water storage. The results showed that soil water storage decreased with increasing afforestation ages and soil depth. Salix matsudana mainly consumed shallow soil water (0–100 cm), P. cathayana mainly consumed deep soil water (100–150 cm), while S. japonica had relatively lower water consumption than the other two species. Converting cropland into forest resulted in a significant water deficit. Soil water deficit in the 0–100 cm soil profiles was significantly higher under S. matsudana than under the other two artificial forests. Severe soil water depletion and obvious soil desiccation occurred after 12 years of afforestation. Therefore, artificial forests with less water consumption, e.g. S. japonica, should be given priority in future afforestation practice. To maintain the sustainability of vegetation, changes in land-use patterns should be considered after 12 years of afforestation.

The spatial variability of soil water storage and its controlling factors during dry and wet periods on loess hillslopes

Soil water storage (SWS), a critical parameter in hydrological processes, is an effective water source for vegetation growth in the semi-arid Loess Plateau of China. Its spatial pattern at various soil depths along transects and temporal changes in the dominant environmental factors that affect SWS are essential to ensure the sustainability of vegetation restoration efforts and achieve an accurate understanding of hydrological processes on the Loess hillslope. In this study, we investigated SWS at depths of 0–4m at a total of 54 points on three hillslopes covered with artificial forest, natural forest and natural grass during four observation periods. The results reflected clear seasonal trends in SWS. A substantial water deficit occurred during the severe drought year of 2015. SWS at depths of 0–1m increased and SWS at depths of 1–4m decreased from after the rainy season of 2015 to before the rainy season of 2016 (a near-normal drought year), and SWS at depths of 0–4m maintained its resemblance to conditions that occurred during the rainy season of 2016. These results may indicate that drought conditions affect variations in SWS. In addition, topography and vegetation type were the dominant factors controlling SWS in the different soil layers. SWS at shallow soil depths was mainly affected by topography, while SWS at deep soil depths was mainly controlled by vegetation type. During the dry season, slope aspect was the most important factor controlling SWS at shallow soil depths due to the effects of slope aspect on snowmelt and wind evaporation. On the other hand, during the wet season, the slope gradient was more important in terms of its effect on SWS than slope aspect at shallow soil depths due to the effects of slope gradient on infiltration and runoff.

Spatiotemporal Characteristics of Soilwater Storage Along Regional Transect on the Loess Plateau, China

Knowledge of the spatiotemporal variability of soil water storage (SWS) is important for vegetation restoration and water resources optimization in semi‐arid areas. This study investigated the spatiotemporal characteristics of SWS in the 0–5 m profile and identified representative sites for reliably estimating the mean SWS along regional transect of the Loess Plateau. Mean relative difference and the associated standard deviation (SDRD) were used to assess temporal stability (TS) of profile SWS. The time‐averaged mean SWS in the 5‐m profile generally decreased from south to north following the decreasing rainfall gradient, with a mean value of 704 mm. Spatiotemporal analysis showed that temporal variations in SWS decreased with increasing soil depth, while the spatial variations increased. Comparisons of SDRD and the number of time‐stable locations with SDRD &lt;5% among various depths indicated that TS increased with increasing soil depth. The representative sites identified for the transect well reflected mean SWS of the five soil layers, and the accuracy of estimation increased with increasing soil depth. The TS of SWS patterns was controlled by precipitation, temperature, clay content, field capacity, soil organic carbon, elevation, slope gradient, and normalized difference vegetation index in the study area. This study demonstrates the feasibility of directly estimating the patterns of SWS using TS analysis on a large scale, which might be comprehensively controlled by the combined effects of climate, soil, topography, and vegetation.

English

In comparison to a measured field water balance (FWB), we aimed to evaluate the impact of using different functions to daily estimate the crop coefficient (Kc) and soil water depletion fraction (p) in a climatological water balance (CWB), and verify that the grouping of output variables provides improved results. The FWB was conducted in Telemaco Borba, Southern Brazil. The data were collected at weekly intervals in 2009, in an area of loblolly pine with 6 years-old. The CWB considers different equations to estimate daily Kc and p values. The output components of the CWB were estimated daily, then weekly and monthly grouped for comparison with the FWB. Linear correlation analysis, index “d” of concordance, index “c” of performance, mean error, mean absolute error and root mean square error were performed in order to compare the water balances, based on the soil-water storage variation (DS) and actual evapotranspiration (ETa). The use of a Kc measured weekly improved the CWB, providing high correlation and small errors in relation to a measured water balance, independent of the comparison scale. On the other hand, the use of a Kc that considers climate variables (Kck) had the worst levels of accuracy and precision, and the biggest mistakes in all analyzes and all tested variables. There was no significant improvement with the daily variation of p, both grouping weeks as in months. The proposed equations do not represent any gain in the CWB, in comparison with the use of a constant p value over time. The estimate of the CWB and its subsequent grouping in months for comparison provided greater degree of accuracy and precision for the variables analyzed, but caused the biggest mistakes. Therefore, the calculation of CWB should be performed with the highest periodicity possible, and grouping the CWB output variables should only be performed for comparison. Key words: Pinus taeda, crop evapotranspiration, actual evapotranspiration, soil water storage, field water balance.

Effects of gullies on the spatiotemporal variability of soil-water under different vegetation types on the Loess Plateau

Gullies are pervasive topographic features on the Loess Plateau. We selected two typical gullies in the water-wind erosion region of the plateau to study the effect of gullies on the spatiotemporal variability of soil-water. The distribution and variation of soil-water storage were evaluated using time-series analysis and classical statistical methods. Soil-water storage varied with distance to the gully borders. The spatial average soil-water in the study sites was 300 cm from the border. soil-water in the vertical direction was mostly dependent on the vegetation, and the gullies had little impact. The spatial distribution of soil-water at a slope scale presented different patterns. Strong upland winds increased the evaporation of soil-water, which rapidly dissipated. Soil-water storage at mid-slope near the gullies was as high as 949.9 mm. The bottom of the slopes had soil-water deficits of 4%. Soil-water storage was much higher in an apricot orchard than in shrubland dominated by Caragana korshinskii Kom. Soil evaporation, vegetation type, and the gullies increased the complexity of the pattern of soil-water.

광릉 산지사면에서의 선행강우지수와 토양저류량 비교연구

The temporal variation of soil water storage is important in hydrological modeling. In order to evaluate an antecedent wetness state, the antecedent precipitation index (API) has been used. The aim of this article is to compare observed soil water storage with APIs calculated by widely used four equations, to configure the relationship between soil water storage and API by a regression model for one-year(2009), and to predict the soil water storage for the next two years(2010～2011). The soil water storage was evaluated from the observed soil moisture dataset in soil depths of 10, 30, 60cm at 21 locations by TDR measurement system for 3 years. As a result, API with the exponential function among the four equations can describe the variation of the observed soil water storage. Monthly optimized parameters of the API’s equations seemed to be roughly related with the (potential) evapotranspiration (PET). Using revised monthly optimized parameters of APIs considering the seasonal pattern of PET, we characterize the relationship between API and the observed soil water storage for one year, which looks better than those of other researches.

Decadal predictability of soil water, vegetation, and wildfire frequency over North America

The potential decadal predictability of land hydrological and biogeochemical variables in North America is examined using a 900-year-long pre-industrial control simulation, conducted with the NCAR Community Earth System Model (CESM) version 1.0.3. The leading modes of simulated North American precipitation and soil water storage are characterized essentially by qualitatively similar meridional seesaw patterns associated with the activity of the westerly jet. Whereas the corresponding precipitation variability can be described as a white noise stochastic process, power spectra of vertically integrated soil water exhibit significant redness on timescales of years to decades, since the predictability of soil water storage arises mostly from the integration of precipitation variability. As a result, damped persistence hindcasts following a 1st order Markov process are skillful with lead times of up to several years. This potential multi-year skill estimate is consistent with ensemble hindcasts conducted with the CESM for various initial conditions. Our control simulation further suggests that decadal variations in soil water storage also affect vegetation and wildfire occurrences. The long-term potential predictability of soil water variations in combination with the slow regrowth of vegetation after major disruptions leads to enhanced predictability on decadal timescales for vegetation, terrestrial carbon stock, and fire frequency, in particular in the Southern United States (US)/Mexico region. By contrast, the prediction skill of fire frequency in the Northern US is limited to 1 year. Our results demonstrate that skillful decadal predictions of soil water storage, carbon stock, and fire frequency are feasible with proper initialization of soil conditions. Although the potential predictability in our idealized modeling framework would overestimate the real predictability of the coupled climate-land-vegetation system, the decadal climate prediction may become beneficial for water resource management, forestry, and agriculture.

Fluxos de água no consórcio milho-pastagem na microbacia hidrográfica do Rio Mundaú, Pernambuco

In the context of world climate changes, the quantification of evapotranspiration (ET) of crops and grasslands is extremely important to anticipate how these changes will affect the hydrological cycle. Many researches were made to measurement of ET ongrasslands; however, there are few researches that measured ET and another soil water balance components in maize-pasture intercropping. The objective of this study was to assess the soil water balance components (soil water storage variations, drainage, capillary rise and evapotranspiration) of the maize-pasture intercropping under rainfed in the catchment Rio Mundau, Pernambuco State.The study was carried out in an experimental area located at the “Riacho do Papagaio” farm(8o 52’ 30’’ S, 36o 22’ 00’’ Wand 705 m), county of Sao Joao, from 01/01/2013 to 31/12/2013. TDR probes to measure the soil water content were installed at depths of 0.10, 0.20, 0.30 and 0.40 m. Rainfall was monitored with rain gauge installed on a tower at the center of the area. For the determination of drainage and capillary rise, infiltration tests were performed in field to obtain the saturated hydraulic conductivity. The soil water retention curve was determined in laboratory. The ETo was obtained by the Penman-Monteith method. It was observed that substantial soil water storage and ET values occurred in the high rainfall periods. The ET throughout the experimental period was the main water outlet of system with a total value of 406.8 mm and average of 1.1 mm d-1.The mean values of ET for periods with bare soil, maize-pasture intercropping and pasture alone were 0.8, 1.5 and 1.1 mm d-1, respectively. The maize-pasture intercropping must have suffered water stress, in almost all experimental period, due the values of the ratio ET/ETo being lower than the 1. The best period for the development of the forages (grasslands and maize) in the region is from april to august

Temporal stability analysis for estimating spatial mean soil water storage and deep percolation in irrigated maize crops

The temporal stability of soil moisture in irrigated cropland may have profound implications for precision agriculture in arid regions. This study evaluated the temporal variation of components of the soil water balance in irrigated cropland in northwestern China and identified representative locations to reliably estimate the profiles (0–1 and 1–2m) of spatial mean soil water storage (SWS) and deep percolation below a depth of 2m. Soil water storages were determined with a neutron probe at 48 locations (31 and 17 in the northern and southern croplands, respectively) on a total of 18 occasions in 2011 and 2012. Crop evapotranspiration, SWS variations and deep percolation were analyzed during the maize growing seasons. Soil water storages in the northern and southern croplands were temporally stable. The location with the lowest standard deviation of relative differences could accurately estimate the spatial mean SWS with a high coefficient of determination (R2>0.91, P<0.001) and prediction accuracy (PE>0.76) and near-zero mean absolute relative error (MARE=0). The most representative locations were different for the 0–1 and 1–2m soil layers, but the location for the 0–1m layer could also generally represent SWS in the 1–2m layer in the northern and southern croplands. From 21 May to late September in both years, approximately 39 and 22% of the irrigation and rainwater were lost as deep percolation in the northern and southern croplands, respectively. Deep percolation at the most representative locations of spatial mean SWS for the 0–1m layers could generally estimate the spatial mean deep percolation below a depth of 2m. This study provides an alternative approach for estimating spatial mean SWS and deep percolation, which is essential for the rational management of scarce resources of irrigation water in a large arid region of northwestern China.