scholarly journals Using StorAge Selection functions to quantify ecohydrological controls on the time-variant age of evapotranspiration, soil water, and recharge

2018 ◽  
Author(s):  
Aaron A. Smith ◽  
Doerthe Tetzlaff ◽  
Chris Soulsby
Keyword(s):  
Soil Moisture ◽  
Surface Water ◽  
Soil Water ◽  
Water Uptake ◽  
Root Water Uptake ◽  
Soil Evaporation ◽  
Root Uptake ◽  
Water Fluxes ◽  
Near Surface ◽  
Moisture Conditions

Abstract. Quantifying ecohydrological controls on soil water availability is essential to understand temporal variations in catchment storage. Soil water is subject to numerous time-variable fluxes (evaporation, root-uptake, and recharge), each with different water ages which in turn affect the age of water in storage. Here, we adapt StorAge Selection (SAS) function theory to investigate water flow in soils and identify soil evaporation and root-water uptake sources from depth. We use this to quantify the effects of soil-vegetation interactions on the inter-relationships between water fluxes, storage, and age. The novel modification of the SAS function framework is tested against empirical data from two contrasting soil-vegetation units in the Scottish Highlands; these are characterised by significant preferential flow, transporting younger water through the soil during high soil moisture conditions. Dominant young water fluxes, along with relatively low rainfall intensities, explain relatively stable soil water ages through time and with depth. Soil evaporation sources were more time-invariant with high preference for near-surface water, independent of soil moisture conditions, and resulting in soil evaporation water ages similar to near-surface soil waters (mean age: 50–65 days). Sources of root-water uptake were more variable: preferential near-surface water uptake occurred in wet conditions, with a deeper root-uptake source during dry soil conditions, which resulted in more variable water ages of transpiration (mean age: 56–79 days). The simple model structure provides a parsimonious means of constraining the water age of multiple fluxes from the upper part of the critical zone during time-varying conditions improving our understanding of vegetation influences on catchment scale water fluxes.

scholarly journals How to put plant root uptake into a soil water flow model

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 43
Author(s):  
Xuejun Dong
Keyword(s):  
Water Stress ◽  
Soil Water ◽  
Water Uptake ◽  
Root Distribution ◽  
Plant Root ◽  
Root Water Uptake ◽  
Root Uptake ◽  
Water Dynamics ◽  
Rooting Depth ◽  
Plant Root Uptake

The need for improved crop water use efficiency calls for flexible modeling platforms to implement new ideas in plant root uptake and its regulation mechanisms. This paper documents the details of modifying a soil infiltration and redistribution model to include (a) dynamic root growth, (b) non-uniform root distribution and water uptake, (c) the effect of water stress on plant water uptake, and (d) soil evaporation. The paper also demonstrates strategies of using the modified model to simulate soil water dynamics and plant transpiration considering different sensitivity of plants to soil dryness and different mechanisms of root water uptake. In particular, the flexibility of simulating various degrees of compensated uptake (whereby plants tend to maintain potential transpiration under mild water stress) is emphasized. The paper also describes how to estimate unknown root distribution and rooting depth parameters by the use of a simulation-based searching method. The full documentation of the computer code will allow further applications and new development.

scholarly journals Modelling root water uptake in a complex land surface scheme coupled to a GCM

1998 ◽  
Vol 2 (2/3) ◽  
pp. 239-255 ◽  
Author(s):  
P. de Rosnay ◽  
J. Polcher
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Water Uptake ◽  
Land Surface ◽  
General Circulation ◽  
Circulation Model ◽  
Root Water Uptake ◽  
Soil Water Storage ◽  
Land Surface Scheme ◽  
Surface Scheme

Abstract. The aim of this paper is to improve the representation of root water uptake in the land surface scheme SECHIBA coupled to the LMD General Circulation Model (GCM). Root water uptake mainly results from the interaction between soil moisture and root profiles. Firstly, one aspect of the soil hydrology in SECHIBA is changed: it is shown that increasing the soil water storage capacity leads to a reduction in the frequency of soil water drought, but enhances the mean evapotranspiration. Secondly, the representation of the soil-vegetation interaction is improved by allowing a different root profile for each type of vegetation. The interaction between sub-grid scale variabilities in soil moisture and vegetation is also studied. The approach consists of allocating a separate soil water column to each vegetation type, thereby 'tiling' the grid square. However, the possibility of choosing the degree of soil moisture spatial heterogeneity is retained. These enhancements of the land surface system are compared within a number of GCM experiments.

scholarly journals Estimating evapotranspiration over vegetated surfaces based on wet patch patterns

2019 ◽  
Vol 50 (4) ◽  
pp. 1037-1046 ◽  
Author(s):  
Peiyuan Li ◽  
Zhi-Hua Wang
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Energy Exchange ◽  
Hydrological Cycle ◽  
Turbulent Transfer ◽  
Near Surface ◽  
Local Climate ◽  
Water Energy Nexus ◽  
Physically Based ◽  
Moisture Conditions

Abstract Evapotranspiration (ET) is a critical component of the hydrological cycle and natural water-energy nexus. The dynamics of soil water content (θ) in the top surface layer, regulated by local climate, predominates the surface energy exchange and ET behavior. In this study, we proposed a novel ET-θ relation using a physically based wet patch radius coupling the near surface turbulent transfer and soil water availability. The model is tested against the dataset from eddy covariance (EC) sites in the AmeriFlux network. The results show that ET rate is supply-driven under low soil moisture conditions since the plant controls the transpiration rate to conserve water due to water stress. While in energy-limited condition, increasing soil moisture will not promote ET rate as it is bounded by the lower atmospheric demand. The proposed method is practically designed to calculate ET using variables readily measured by standard EC towers such as soil moisture and meteorological measurements. The method can also potentially be extended to predict the spatial and physical patterns of ecosystem services under different hydroclimatic conditions.

How to scale root water uptake from root scale to stands and beyond – a theoretical framework, practical lessons, and next steps

2020 ◽  
Author(s):  
Martin Bouda ◽  
Jan Vanderborght ◽  
Valentin Couvreur ◽  
Félicien Meunier ◽  
Mathieu Javaux
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Water Flow ◽  
Water Uptake ◽  
Root Systems ◽  
Root Water Uptake ◽  
Discretization Error ◽  
Persistent Problem ◽  
Plant Hydraulics ◽  
Soil Moisture Heterogeneity

<p>Estimating plant uptake of soil water has been a persistent problem in process-based earth system models (ESMs). Initially ignored altogether, plant access to soil water was long modelled with heuristic approaches at large scales. These formulations are currently being replaced as ESMs begin to incorporate more detailed plant hydraulics schemes based on the soil-plant-atmosphere continuum concept. While the new schemes greatly improve mechanistic description of above-ground plant hydraulics, they have given rise to various issues belowground, from excessive hydraulic redistribution to numerical instability. As detailed 3D descriptions of root systems and water flow equations on the soil-root domain have been established, the key challenge is how to scale them up to relevant scales, reducing computational cost to a trivial level without loss of accuracy.</p><p>Here, we set out a mathematical framework that incorporates recent advances in this area and allows us to relate them to each other. Comparing and contrasting different models, formulated in a novel matrix form of the water flow problem in the root system, allows us to make inferences about their suitability for use in upscaling. We are able to show how to avoid discretization error in the upscaled root scheme, as well as which upscaling method offers full generality, and which yields the computationally simplest forms. These theoretical results are fully supported by numerical simulations of fully explicit 3D root systems and their upscaled versions. Improved performance of the upscaled models is also demonstrated in an application to field data from the Wind River Crane flux tower site (reduced model bias, root mean squared error, and increased robustness of fitted parameters).</p><p>Root water uptake equations can now be scaled up without discretization error for arbitrary root systems. The chief remaining source of error is soil moisture heterogeneity within discretized soil elements where it is assumed uniform by any given model (e.g. within each vertical layer). The main task for future work thus becomes to achieve a correspondingly accurate description for soil moisture heterogeneity. Some of the upscaling approaches compared here offer hints at potential next steps in this direction.</p>

Detecting crop water requirements indicators in irrigated agro-ecosystems from soil water content profiles: an application for a citrus orchard

2021 ◽  
Author(s):  
Giuseppe Provenzano ◽  
Daniel Alberto Segovia-Cardozo
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Uptake ◽  
Crop Coefficient ◽  
Root Water Uptake ◽  
Climate Variables ◽  
Crop Water ◽  
Citrus Orchard

<p>For annual cropping systems sensitive to water stress, such as citrus, efficient water management can allow facing their large water consumption and enhancing crop sustainability. However, to apply water-saving strategies it is necessary to monitoring soil and/or plant water status. In the last decade, a wide number of sensors providing indirect measurements of volumetric soil water content based on soil physical properties, such as dielectric permittivity or matric potential, have been developed. Among the sensors using the frequency domain reflectometry technique, the “drill and drop” (Sentek, Inc., Stepney, Australia) multi-sensor probes allow continuous acquisition of soil moisture dynamic every 10 cm starting from the soil surface; these data hide important information on root water uptake and actual crop evapotranspiration.</p><p>The objective of the paper was to analyze the temporal dynamics of soil water content profiles detected with multi-sensor probes during three years of field observations (July 2017- August 2020) in a citrus orchard, to estimate root water uptake and crop transpiration by three methodologies. Simultaneous measurements of sap fluxes and climate variables also allowed estimating the basal crop coefficient, K<sub>cb</sub>, often considered for estimating crop water requirement.</p><p>The experiments were carried out in a 30 years-old citrus orchard (C. reticulata Blanco cv. Tardivo di Ciaculli) with trees spaced 5.0x5.0 m. The field is irrigated with a subsurface drip system installed in 2018, with two lateral pipes per plant row at 30 depth and distance of 1.1 m from the trunk. Integrated sensing methodologies supported by the Internet of Things and cloud computing technologies (Agrinet/Tuctronics, Walla Walla, WA, USA), linked with a suitable communication infrastructure, were used to acquire continuously, in real-time and from remote soil water contents and climate variables. Four soil moisture profiles corresponding to as many plants were monitored with 120 cm long drill and drop sensors installed at a distance of 30 cm from one emitter. A standard weather station (Spectrum Technologies, Inc) was also installed to acquire, once every half hour, wind speed and direction at 2 m height, solar radiation, air temperature, relative air humidity and precipitation. In both years, sap fluxes were also measured hourly on two citrus trees, by using two Granier’s thermal dissipation probes (TDP) per tree. Each hour, the difference of temperature between the upper heated and lower un-heated needles, combined with the temperature difference at night allowed to estimate the sap velocity and then the hourly sap fluxes.</p><p>The analysis evidenced the characteristic declines of soil water content after rainfall events, from which it was possible verifying that the hourly dynamic of root water uptake followed that of the corresponding sap flow sensors. Moreover, the knowledge of daily root water uptake, associated with the simultaneous values of reference evapotranspiration allowed obtaining suitable estimations of the basal crop coefficient. The proposed approach provided interesting insights into the dynamic of root water uptake of citrus trees and can represent a promising tool for precise irrigation scheduling.</p>

scholarly journals Analysis of Soil Water Response to Grass Transpiration

2013 ◽  
Vol 1 (No. 3) ◽  
pp. 85-98
Author(s):  
Dohnal Michal ◽  
Dušek Jaromír ◽  
Vogel Tomáš ◽  
Herza Jiří
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Preferential Flow ◽  
Water Movement ◽  
Control Volume ◽  
Water Pressure ◽  
Lower Boundary ◽  
Root Water Uptake ◽  
Water Dynamics ◽  
Soil Water Dynamics

This paper focuses on numerical modelling of soil water movement in response to the root water uptake that is driven by transpiration. The flow of water in a lysimeter, installed at a grass covered hillslope site in a small headwater catchment, is analysed by means of numerical simulation. The lysimeter system provides a well defined control volume with boundary fluxes measured and soil water pressure continuously monitored. The evapotranspiration intensity is estimated by the Penman-Monteith method and compared with the measured lysimeter soil water loss and the simulated root water uptake. Variably saturated flow of water in the lysimeter is simulated using one-dimensional dual-permeability model based on the numerical solution of the Richards’ equation. The availability of water for the root water uptake is determined by the evaluation of the plant water stress function, integrated in the soil water flow model. Different lower boundary conditions are tested to compare the soil water dynamics inside and outside the lysimeter. Special attention is paid to the possible influence of the preferential flow effects on the lysimeter soil water balance. The adopted modelling approach provides a useful and flexible framework for numerical analysis of soil water dynamics in response to the plant transpiration.

scholarly journals Modelling the Impact on Root Water Uptake and Solute Return Flow of Different Drip Irrigation Regimes with Brackish Water

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 425 ◽  
Author(s):  
Fairouz Slama ◽  
Nessrine Zemni ◽  
Fethi Bouksila ◽  
Roberto De Mascellis ◽  
Rachida Bouhlila
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Uptake ◽  
Brackish Water ◽  
Deficit Irrigation ◽  
Root Zone ◽  
Root Water Uptake ◽  
Return Flows ◽  
Semi Arid

Water scarcity and quality degradation represent real threats to economic, social, and environmental development of arid and semi-arid regions. Drip irrigation associated to Deficit Irrigation (DI) has been investigated as a water saving technique. Yet its environmental impacts on soil and groundwater need to be gone into in depth especially when using brackish irrigation water. Soil water content and salinity were monitored in a fully drip irrigated potato plot with brackish water (4.45 dSm−1) in semi-arid Tunisia. The HYDRUS-1D model was used to investigate the effects of different irrigation regimes (deficit irrigation (T1R, 70% ETc), full irrigation (T2R, 100% ETc), and farmer’s schedule (T3R, 237% ETc) on root water uptake, root zone salinity, and solute return flows to groundwater. The simulated values of soil water content (θ) and electrical conductivity of soil solution (ECsw) were in good agreement with the observation values, as indicated by mean RMSE values (≤0.008 m3·m−3, and ≤0.28 dSm−1 for soil water content and ECsw respectively). The results of the different simulation treatments showed that relative yield accounted for 54%, 70%, and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full. and farmer’s irrigation, respectively. Root zone salinity was the lowest and root water uptake was the same with and without solute stress for the treatment corresponding to the farmer’s irrigation schedule (273% ETc). Solute return flows reaching the groundwater were the highest for T3R after two subsequent rainfall seasons. Beyond the water efficiency of DI with brackish water, long term studies need to focus on its impact on soil and groundwater salinization risks under changing climate conditions.

SIMULATING SOIL WATER FLOW WITH ROOT-WATER-UPTAKE APPLYING AN INVERSE METHOD

Soil Science ◽  
2004 ◽  
Vol 169 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Qiang Zuo ◽  
Lei Meng ◽  
Renduo Zhang
Keyword(s):  
Soil Water ◽  
Water Flow ◽  
Water Uptake ◽  
Inverse Method ◽  
Root Water Uptake ◽  
Soil Water Flow

scholarly journals Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

2021 ◽  
Author(s):  
Stefano Materia ◽  
Constantin Ardilouze ◽  
Chloé Prodhomme ◽  
Markus G. Donat ◽  
Marianna Benassi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Soil Water ◽  
Land Surface ◽  
Heat Waves ◽  
Climate Regime ◽  
Seasonal Forecasts ◽  
Near Surface ◽  
Surface Temperatures ◽  
The Mediterranean

AbstractLand surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.

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