The Murrumbidgee soil moisture monitoring network data set

Cosmic-Ray Neutron Sensing (CRNS) delivers an integral value of soil moisture over a radial footprint of 150 to 240 m and a penetration depth of 15 to 83 cm. The support volume, especially in the vertical extent, decreases with increasing soil moisture. As the sensor is most sensitive to upper soil layers and the signal contribution decreases with increasing depth, the vertical distribution of moisture influences the signal received by the neutron detector. Additional soil moisture measurements are required to estimate the penetration depth of the CRNS measurement. These may be provided by profile measurements of a soil moisture monitoring network equipped with buried electromagnetic sensors. Different horizontal and vertical weighting schemes exist to compare the integrated CRNS value to an integrated (weighted) average value from a sensor network by adjusting reference measurements to the spatial sensitivity of the sensor. The vertical weighting was developed based on hydrodynamic modelling of a soil column and a neutron transport model (MCNPx). Since then the development of the Ultra Rapid Adaptable Neutron-Only Simulation (URANOS) opened up the possibilities for more complex neutron simulations to understand and interpret the CRNS signal. Simulations confirmed the large influence of soil moisture on the penetration depth of the sensor for homogeneous vertical soil moisture distributions, rarely occurring in natural environments. While in recent years the influence of horizontal heterogeneities on the signal generation was the focus of several studies, the influence of vertical gradients achieved less attention.Against this background, we evaluate data from a field site in southern Germany with clayey soils and influence of shallow groundwater, where a CRNS is operated in parallel to a soil moisture monitoring network. We observe a good match between the time series of CRNS derived soil moisture and the weighted soil moisture from the sensor network during infiltration events. Several times during summer, however, topsoil dries and a strong vertical gradient develops (0.20 m&#179; m-&#179; in 5 cm to 0.50 m&#179; m-&#179; in 20 cm depth). During these periods the weighted sensor network underestimates CRNS derived soil moisture by up to 0.25 m&#179; m-&#179;. We hypothesize, that the estimation of the penetration depth does not hold for these extreme soil moisture gradients and that neutrons penetrate deeper into the soil and probe the wetter layers. The combination of observed neutron intensities as well as dedicated neutron transport simulations using the URANOS and MNCP6 model code will help to understand the site-specific signal behavior, explain differences observed in the data and lastly, gain information on the behavior of neutron intensities under vertically varying soil moisture contents.

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Feasibility analysis of using inverse modeling for estimating natural groundwater recharge from a large-scale soil moisture monitoring network

Journal of Hydrology ◽

10.1016/j.jhydrol.2015.12.019 ◽

2016 ◽

Vol 533 ◽

pp. 250-265 ◽

Cited By ~ 25

Author(s):

Tiejun Wang ◽

Trenton E. Franz ◽

Weifeng Yue ◽

Jozsef Szilagyi ◽

Vitaly A. Zlotnik ◽

...

Keyword(s):

Soil Moisture ◽

Groundwater Recharge ◽

Inverse Modeling ◽

Large Scale ◽

Monitoring Network ◽

Feasibility Analysis ◽

Soil Moisture Monitoring

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A soil moisture monitoring network to characterize karstic recharge and evapotranspiration at five representative sites across the globe

10.5194/gi-2019-22 ◽

2019 ◽

Cited By ~ 1

Author(s):

Romane Berthelin ◽

Michael Rinderer ◽

Bartolomé Andreo ◽

Andy Baker ◽

Daniela Kilian ◽

...

Keyword(s):

Land Use ◽

Soil Moisture ◽

Land Cover ◽

Groundwater Recharge ◽

Monitoring Network ◽

Land Use Types ◽

Karst Systems ◽

The Impact ◽

Soil Moisture Monitoring ◽

Sequential Reactions

Abstract. Karst systems that are characterized by a high subsurface heterogeneity are posing a challenge to study their complex recharge processes. Experimental methods to study karst processes mostly focus on characterizing the entire aquifer. Despite their important role for recharge processes, the limited focus has been given on studies of the soil and epikarst and most available research has been performed at sites of similar latitudes. In our study, we describe a new monitoring concept that allows the improvement of soil and epikarst processes understanding by covering different karst systems with different land cover at different climate regions. First, we describe the site selection and the experimental setup. Then we describe the five individual sites and their soil profiles. We also present some preliminary data and highlight the potential of the data for future research aimed at answering the relevant research questions: (1) How do the soil and epikarst heterogeneities influence water flow and storage processes in the karst vadose zone? (2) What is the impact of the land cover type on karstic groundwater recharge and evapotranspiration? (3) What is the impact of climate on karstic groundwater recharge and evapotranspiration? In order to answer these questions, we monitor soil moisture, which controls the partitioning of rainfall into infiltration, soil water storage, evapotranspiration, and groundwater recharge processes. We installed a soil moisture-monitoring network at five different climate regions: in Puerto Rico (tropical), Spain (Mediterranean), the United Kingdom (humid oceanic), Germany (humid mountainous), and Australia (dry semi-arid). At each of the five sites, we defined two 20 m × 20 m plots to install soil moisture probes under different land use types (forest and grassland). At each plot, 15 soil moisture profiles were installed with probes at different depths from the top soil to the epikarst (over 400 soil moisture probes were installed). Our first results show that the monitoring network provides new insights into the soil moisture dynamics of the five study sites and that significant differences prevail among forest and grassland sites. Some profiles are characterized by sequential reactions of soil moisture, i.e., the uppermost probe reacts first and the lowest probe reacts last, while at other profiles, we find non-sequential reactions that we interpret to result from preferential flow processes. While the former favours storage in the soil providing water for evapotranspiration, the latter can be seen as an indicator for the initiation of fast and preferential recharge into the karst system. Covering the spatiotemporal variability of these processes through a large number of installed probes, our monitoring network will allow to develop a new conceptual understanding of evapotranspiration and groundwater recharge processes in karst regions across different climate regions and land use types, and provide the base for quantitative assessment with physically-based modelling approaches in the future.

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Towards establishing an Irish National Soil Moisture Monitoring Network

10.5194/ems2021-273 ◽

2021 ◽

Author(s):

Tamara Hochstrasser ◽

Caren Jarmain ◽

Klara Finkele ◽

Paul Murphy ◽

Owen Fenton ◽

...

Keyword(s):

Soil Moisture ◽

Land Surface ◽

Research Question ◽

Monitoring Network ◽

Hydrologic Cycle ◽

Consultation Process ◽

Ongoing Research ◽

Starting Point ◽

Soil Moisture Monitoring

The hydrologic cycle is currently being altered due to climate change and the potential impacts are diverse. Long-term monitoring of the components of this cycle will aid our understanding of these changes. Soil moisture is one of the components often neglected, with few long-term datasets available. It is an important variable, regulating the exchange of water and heat energy between the land surface and the atmosphere through evaporation and plant transpiration. Our understanding of soil moisture dynamics is often limited, and an expansion of the current monitoring network holds many benefits. Recently, a process was initiated to establish an effective Irish National Soil Moisture Monitoring Network. This network aims to be research question driven, consistent in its measurement approach and designed to be useful for ongoing research. Here we report on the consultation process that started in early 2020 within the Irish Agmet group, a working group on Agrometeorology. Specifically, we (1) provide background to the consultation process that showed widespread support for a long-term soil moisture monitoring network which led to funding applications to establish this network, (2) review initiatives underway to monitor soil moisture and other components of the hydrologic cycle and highlight the benefits of long-term widespread measurements to various initiatives and sectors, (3) suggest new and novel monitoring technologies that will be investigated and (4) provide an implementation strategy for what is anticipated to be an efficient and successful network. The paper should serve as a starting point to obtaining widespread support for a national hydro-climate monitoring network.

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