Exploring the role of soil storage capacity for explaining deviations from the Budyko curve using a simple water balance model

The Budyko curve is a widely used framework for predicting the steady-state water balance –solely based on the hydro-climatic setting of river basins. While this framework has been tested and verified across a wide range of climates and settings around the globe, numerous catchments have been reported to considerably deviate from the predicted behavior. Here, we hypothesize that storage capacity and field capacity of the root zone are important controls of the water limitation of evapotranspiration and thus deviations of the mean annual water balance from the Budyko curve. For testing our hypothesis, we selected 16 catchments of different climatic settings and varied the corresponding parameters of a simple water balance model that was previously calibrated against long-term data and investigated the corresponding variations of the simulated water balance in the Budyko space. We found that total soil storage capacity –by controlling water availability and limitation of evapotranspiration– explains deviations of the evaporation ratio (EVR) from the Budyko curve. Similarly, however to a lesser extent, the evaporation ratio showed sensitivity to alterations of the field capacity. In most cases, the parameter variations generated evaporation ratios enveloping the Budyko curve. The distinct soil storage volumes that matched the Budyko curve clustered at a normalized storage capacity equivalent to 5–15 % of mean annual precipitation. The second, capillarity-related soil parameter clustered at around 0.6–0.8, which is in line with its hydropedological interpretation. A simultaneous variation of both parameters provided additional insights into the interrelation of both parameters and their joint control on offsets from the Budyko curve. Here we found three different sensitivity patterns and we conclude the study with a reflection relating these offsets to the concept of catchment coevolution. The results of this study could also be useful to facilitate evaluation of the water balance in data-scarce regions, as they help constrain parameterizations for hydrological models a priori using the Budyko curve as a predictor.

Revisiting soil bacterial counting methods: Optimal soil storage and pretreatment methods and comparison of culture-dependent and -independent methods

Although a number of different methods have been used to quantify soil bacteria, identifying the optimal method(s) for soil bacterial abundance is still in question. No single method exists for undertaking an absolute microbial count using culture-dependent methods (CDMs) or even culture-independent methods (CIMs). This study investigated soil storage and pretreatment methods for optimal bacterial counts. Appropriate storage temperature (4°C) and optimal pretreatment methods (sonication time for 3 min and centrifugation at 1400 g) were necessary to preserve bacterial cell viability and eliminate interference from soil particles. To better estimate soil bacterial numbers under various cellular state and respiration, this study also evaluated three CDMs (i.e., colony forming unit, spotting, and most probable number (MPN) and three CIMs (i.e., flow cytometry (FCM), epifluorescence microscopy (EM) count, and DNA quantitation). Each counting method was tested using 72 soil samples collected from a local arable farm site at three different depths (i.e., 10–20, 90–100, and 180–190 cm). Among all CDMs, MPN was found to be rapid, simple, and reliable. However, the number of bacteria quantified by MPN was 1–2 orders lower than that quantified by CIMs, likely due to the inability of MPN to count anaerobic bacteria. The DNA quantitation method appeared to overestimate soil bacterial numbers, which may be attributed to DNA from dead bacteria and free DNA in the soil matrix. FCM was found to be ineffective in counting soil bacteria as it was difficult to separate the bacterial cells from the soil particles. Dyes used in FCM stained the bacterial DNA and clay particles. The EM count was deemed a highly effective method as it provided information on soil mineral particles, live bacteria, and dead bacteria; however, it was a time-consuming and labor-intensive process. Combining both types of methods was considered the best approach to acquire better information on the characteristics of indigenous soil microorganisms (aerobic versus anaerobic, live versus dead).

The technology of laying bentonite mats on the canal under difficult conditions of work performance

Purpose: the technology of laying geocomposite bentonite mats with the creation of an anti-filtration lining of increased reliability on the main canal section made under difficult conditions (in the presence of karst and suffusion phenomena) is considered. Materials and methods. The theoretical basis of the research is the indicators of physical, mechanical and technical characteristics of bentonite mats of various manufacturing companies. The practical component is flow charts, diagrams and technology for the work performance in natural conditions on the main canal section. Results and discussion: to reduce the filtration coefficient of anti-filtration coatings it is advisable to use two- and three-layer materials, which were used in the reconstruction of the Donskoy main canal section instead of polymeric materials, according to the results of the feasibility study. The work on laying sodium bentonite mats was carried out in difficult conditions after stopping the water supply, when there was an intense slope sloughing, and the water level in the canal was set below the groundwater level in the canal zone. At the same time, the canal was periodically cleaned with a dredger to remove the swollen soil along the canal bottom, and on the slopes – excavation with a dragline excavator, followed by transportation and soil storage in the slurry dump maps. Further, the work was carried out on maps with pools, separated by dams, where map sections were drained by a mobile pumping station. Conclusions: the use of the developed technology for canal cleaning and laying roll materials based on bentonite made it possible to reconstruct successfully the most dangerous canal sections. The introduction of a structural and technical solution in the form of a combined screen design ensures almost complete water imperviousity of the bottom and slopes of the canal.

Research on displacement prediction of shield tunneling through existing tunnel based on LSSVM

The construction scale of the shield tunnel underpass is expanding day by day. In order to study the safety influence and deformation control of the shield tunnel underpass on the existing tunnel, the LSSVM model is established. Based on the collected soil storage pressure, foam volume, simultaneous grouting volume and other six shield construction parameters and corresponding sample data of the tunnel bottom displacement, the horizontal displacement and settlement displacement of the existing tunnel bottom caused by the approach construction are predicted. Taking a subway project as an example, the research results show that the prediction model of shield tunneling under the existing tunnel bottom level and settlement displacement has strong generalization ability and rapid and accurate prediction effect. This method can provide reference for similar projects.

Carbon content in a system of avocado production (Persea americana Mill) in Pillco marca - Huánuco - 2018.

The investigation was carried out in a system of avocado production (Persea americana Mill) var. Has and strong, politically located in the Center for Fruit and Fruit Research (CIFO) - Huanuco. In order to determine the content of organic carbon (COS) at three depths of the soil and estimate the carbon fixed in the aerial and underground biomass of avocado plants by using allometric equations. The methodology used for the field sampling process of probabilistic COS in its Composite Random Sampling form, while for aerial and underground biomes in its optimal stratified sampling form. It was determined that the storage of total organic carbon in the soil by surface between plant and under the tree from 0 to 10 cm deep presents the lowest tendency to store less carbon 9.45 and 10.37 t C/ha respectively. However, as soil depth increases, the rate of organic carbon fixation in the soil tends to increase 17.79 and 10.98 t C/ha from 20 to 30 cm deep. As well as the area and underground biomass of the avocado plants of 7 years of age. The avocado evaluated reached storing 30,239 t C/ha in the aerial biomass and 6,918 t C/ha in the underground biomass. The carbon fixation rate in avocado plants to date stores 5,308 t/ha in total biomass. Keywords: Organic carbon, soil, storage, biomass, fixation rate.

Post-earthquake changes in debris flow susceptibility in the Upper Minjiang catchment (Sichuan, China), as revealed by meteorological and hydro-meteorological thresholds

<p>On May 12, 2008, a Mw 7.9 earthquake struck Wenchuan, Longmen Shan Area, in western Sichuan, China, at the eastern margin of the Tibetan Plateau. This earthquake was the largest and most destructive event in the last 60 years, causing more than 87000 casualties. The economic loss was estimated at some 1100 billion RMB. The major fault rupture produced surface displacements up to 3-4 meters, spreading from the epicenter (near the town of Yingxiu) for 240 km along the mountain range.</p><p>The Wenchuan Earthquake triggered almost 200000 co-seismic landslides over a region larger than 110000 km<sup>2</sup>, leading to the accumulation of large volumes of loose material either along slopes or in gullies. After the earthquake, this material caused a strong increase of debris flow occurrence in the subsequent years, mainly in the worst-hit areas, such as Wenchuan, Beichuan and Mao counties. During the years immediately after the earthquake, the rainfall required for debris flow triggering resulted clearly smaller than before (Guo et al., 2016). Afterwards, the response of the debris deposits to rainfall changed, leading to a general recovery of stability and a reduction of debris flow frequency and magnitude (Domènech et al., 2019).</p><p>In this study, the assessment of debris flows occurrence throughout upper Minjiang catchment, to which Wenchuan county belongs, is modeled with two empirical approaches, both based on the available record of precipitations and debris flows in the years 2008-2015. In the first approach, a threshold to predict debris flow occurrence is defined based on intensity and duration of potentially triggering rainfall events (meteorological threshold). With the second approach, also the hydrological conditions predisposing the slopes to debris flows are considered, by assessing the water balance in the catchment with a simplified lumped hydrological model, based on the Budyko framework (Zhang et al., 2008), and defining a threshold to predict debris flows based on rainfall depth and estimated soil storage prior the onset of rainfall (hydro-meteorological threshold).</p><p>The obtained results indicate that the hydro-meteorological threshold allows catching the progressive recovery of stability of the debris deposits much better than the meteorological threshold, leading to identification of increasing thresholds, both in terms of pre-event soil storage and triggering rainfall amount, in the years from 2008 onward. Such a result shows that the adoption of process-based approaches , even empirical and strongly simplified as in the presented case, leads to predictions of debris flow occurrence more robust than those based solely on rainfall information.</p><p> </p><p>References</p><p>Domènech, G., Fan, X., Scaringi, G., van Asch, T.W.J., Xu, Q., Huang, R., Hales, T.C., 2019. Modelling the role of material depletion, grain coarsening and revegetation in debris flow occurrences after the 2008 Wenchuan earthquake. Eng. Geol. 250, 34-44.</p><p>Guo, X., Cui, P., Li, Y., Fan, J., Yan, Y., Ge, Y., 2016. Temporal differentiation of rainfall thresholds for debris flows in Wenchuan earthquake-affected areas. Environ. Earth Sci. 75, 1–12.</p><p>Zhang, L., Potter, N., Hickel, K., Zhang, Y., Shao, Q., 2008. Water balance modeling over variable time scales based on the Budyko framework – Model development and testing. J. Hydrol. 360, 117-131.</p>

Use of laser spectroscopy to evaluate the influence of soil storage on N2O emission

<p>Accurate measurements of nitrous oxide (N<sub>2</sub>O) fluxes from soils are necessary to understand dynamic changes in soil nitrogen cycles. Laboratory incubation experiments provide a controlled condition to measure these N<sub>2</sub>O fluxes. Before incubation experiments, soils are often stored at certain conditions to minimize the microbial activities. However, the effect of soil storage on N<sub>2</sub>O emission has been poorly studied. A laboratory incubation experiment was conducted using disturbed soils to study the storage effect. The soil was sieved to 2mm and the following four treatments were tested: fresh undisturbed (FU), fresh sieved (FS), fridge stored at 4ºC (ST), and stored at room temperature after drying (PI). After soil samples were brought to 60% water-filled pore space (WFPS), <sup>15</sup>N labelled urea (1 At%) was applied at the rate of 50 mg N kg<sup>-1</sup> soil and the soil was incubated at room temperature (23 ºC). The N<sub>2</sub>O fluxes were measured for 7 weeks using off-axis integrated cavity output spectroscopy (OA-ICOS, Los Gatos Research, California, USA). Cumulative N<sub>2</sub>O fluxes and Keeling plot intercepts (δ<sup>15</sup>N source) were calculated. The results showed that soil storage has a significant effect on N<sub>2</sub>O emission. Over the 7-week period, ST produced the highest cumulative N<sub>2</sub>O emissions (2.70 µg N g<sup>-1</sup> soil) as well as the largest amount of N derived from fertiliser (Ndff) (1.4 µg N g<sup>-1</sup> soil). FU produced the lowest cumulative N<sub>2</sub>O emissions (1.0 µg N g<sup>-1</sup> soil) but the largest amount of N derived from soil (Ndfs) (0.6 µg N g<sup>-1</sup> soil). The daily N<sub>2</sub>O fluxes of FS and FU declined rapidly after the peak emissions, but the fluxes of PI and ST fluctuated after the peaks. These results indicate that soil storage affects microbial processes and therefore N<sub>2</sub>O emissions. Our results suggest using fresh soil to avoid storage effects. If this is not possible the effect of soil storage should be considered before the experiment.  </p>