Water Level Variations Research Articles

Technical note: High-density mapping of regional groundwater tables with steady-state surface nuclear magnetic resonance – three Danish case studies

Abstract. Groundwater is an essential part of the water supply worldwide, and the demands on this water source can be expected to increase in the future. To satisfy the need for resources and to ensure sustainable use of resources, increasingly detailed knowledge of groundwater systems is necessary. However, it is difficult to directly map groundwater with well-established geophysical methods as these are sensitive to both lithology and pore fluid. Surface nuclear magnetic resonance (SNMR) is the only method with a direct sensitivity to water, and it is capable of non-invasively quantifying water content and porosity in the subsurface. Despite these attractive features, SNMR has not been widely adopted in hydrological research, the main reason being an often-poor signal-to-noise ratio, which leads to long acquisition times and high uncertainty in terms of results. Recent advances in SNMR acquisition protocols based on a novel steady-state approach have demonstrated the capability of acquiring high-quality data much faster than previously possible. In turn, this has enabled high-density groundwater mapping with SNMR. We demonstrate the applicability of the new steady-state scheme in three field campaigns in Denmark, where more than 100 SNMR soundings were conducted with a depth of investigation of approximately 30 m. We show how the SNMR soundings enable us to track water level variations at the regional scale, and we demonstrate a high correlation between water levels obtained from SNMR data and water levels measured in boreholes. We also interpret the SNMR results jointly with independent transient electromagnetic (TEM) data, which allows us to identify regions with water bound in small pores. Field practice and SNMR acquisition protocols were optimized during the campaigns, and we now routinely measure high-quality data at 8 to 10 sites per day with a two-person field crew. Together, the results from the three surveys demonstrate that, with steady-state SNMR, it is now possible to map regional variations in water levels with high-quality data and short acquisition times.

Unraveling the synergistic effects of microbes and selenium in alleviating drought stress in Camelina sativa L.

Globally, drought has emerged as one of the most serious threats to oil seed crops including Camelina production, which necessitates screening of drought resistant cultivars that are more responsive to mitigation treatments. Effect of microbes and Selenium (Se) is associated with the upregulation of available nutrients. Therefore, present study was aimed to evaluate the effect of Se interactions with arbuscular mycorrhizal fungi Rhizophagus intraradices at four different treatments (T1: CK), T2: inoculation of R. intraradices), T3: Se-priming (2 mM), T4: inoculation of R. intraradices+ Se-priming (2 mM) on two Camelina genotypes (Australian and Canadian) under varied water levels (100%, 75%, 50%, and 25% field capacity, FC). Se with Seed priming and microbes were applied through inoculation of Camelina seed. The experiment was conducted in a Completely Randomized Design (CRD) with three replications at MNS- University of Agriculture Multan, Pakistan. The results exhibited that inoculation of R. intraradices + Se-priming (2 mM) application significantly improved the physiological and growth parameters of Camelina under water stress. The application of inoculation of R. intraradices + Se-priming (2 mM) increased crop growth, physiology, and antioxidants as compared to other treatments (T1: (Control), T2: Microbes (R. intraradices), T3: Se-priming (2 mM). The application of Microbes + Se-priming (2 mM) increased the total soluble sugars by 69.6%, 23.4%, and 10.8% as compared to other treatments (T1: (Control), T2: inoculation of R. intraradices), T3: Se-priming (2 mM)., respectively, irrespective of field capacity levels. Among varied water levels, 100% FC showed unmatched results regarding crop growth traits, physiological aspects, and antioxidants activities as compared to water stressed levels of 75%, 50%, and 25% FCs. Proline contents were also increased by 93.9%, 52.5%, and 10.2% at 100% FC as compared to 25%, 50%, and 75% FCs. The response of Canadian Camelina was found better than Australian Camelina in most of the growth, physiological, and antioxidant parameters. Canadian Camelina also showed a 2.14% increase in superoxide dismutase activity as compared to Australian Camelina. The combination of Canadian Camelina inoculation of R. intraradices + Se-priming (2 mM) is recommended to achieve higher productivity under water-stressed conditions. However, long-term studies must be conducted to screen out drought resistant and inoculation of R. intraradices + Se-priming responsive genotypes for increasing Camelina yield in low input farming systems. Further, Se-mediated physiological and biochemical associated with drought tolerance in Camelina plants and future research prospects have been elucidated.

The Global Drivers of Chronic Coastal Flood Hazards Under Sea‐Level Rise

AbstractWe present the first global estimates of annual average exceedances of contemporary minor, moderate, and major flood levels under sea‐level rise (SLR). Applying established methods, we show that minor flooding will occur most days worldwide under 0.7 m global SLR. Moderate flooding occurs at the same frequency under 1.0 m SLR. Local and regional differences in flood threshold elevations, tidal ranges, and non‐tidal variability lead to differences in the SLR required for this chronic flooding to emerge. Lower flood thresholds, smaller tidal ranges, and larger extreme skew surges mean chronic flooding can emerge with less SLR. We discuss several implications of these findings for coastal flood hazard assessments. First, tide‐driven water level variability dominates weather‐driven water level variability when determining locations' propensities for frequent and chronic flooding under SLR. Second, centimeter‐accurate flood threshold information is necessary to accurately estimate present and future flood hazards. Third, locations with the most frequent floods at present may not be those that have the most frequent floods under SLR. We develop the Rapid Assessment Framework for Frequent Flood Transitions under SLR (RAFFFTS) to apply these findings to locations not previously considered in global coastal flood hazard studies. RAFFFTS can robustly identify potential future tidal flooding hotspots using only 1‐year observational records. We anticipate RAFFFTS will be a valuable tool for identifying locations at risk of chronic flooding under SLR, complementing existing tools for identifying changes in less frequent episodic floods.

Optimistic Scenario of 0.50 m Mean Sea Level Rise and Possible Environmental Impacts, Resulting from Tidal Variations, in the City of Niterói, Rio de Janeiro—Brazil

As several researches indicate, since the 1950s one observed unprecedented warming of the atmosphere and oceans, resulting from greenhouse gas emissions and changes in land use and occupation, leading to sea level rise and impacts on coastal areas. In the municipality of Niterói—Rio de Janeiro, Brazil, where a large urban concentration in coastal areas is observed, a Climate Change Adaptation System was developed, through which mitigation and adaptation strategies are combined, in order to: reduce vulnerabilities; avoid losses and damages; build instruments to allow adaptation of natural, human, productive and infrastructure systems. In this context, this paper aims to measure possible impacts, in the biophysical and socioeconomic spheres, resulting from an eventual 0.50 m rise in mean sea level, which represents an optimistic scenario according to the National Oceanic and Atmospheric Administration. In contrast to similar studies, this work also considered daily and occasional water level variations, represented by the highest astronomical tide and the highest storm surge observed in the studied region. The following data were applied: digital elevation model, 2010 population census data, and real estate information. With the altimetry data, by means of GIS, the census sectors inserted in the affected areas were selected, to obtain data regarding population, number of households, and income. Specialized websites were applied to collect average property values. The simulations revealed that approximately 2950 households and more than 9000 residents could be directly affected, with losses that could exceed R$ 3.60 billion. The Oceanic Region is configured as the most exposed region, susceptible to losses of several ecosystems, economic losses in residential areas and possible destruction of urban infrastructure.

Extreme Droughts and Their Relationship with the Interdecadal Pacific Oscillation in the Peruvian Altiplano Region over the Last 100 Years

The Peruvian Altiplano Region (RAP) is a high plateau area surrounded by the Western and Eastern Andes mountain ranges. This study examines the relationship between extreme droughts in the region and the interdecadal Pacific Oscillation (IPO) over the past century. Previous research has shown that precipitation patterns in the region follow a decreasing trend, with systematic increases in precipitation on the western slope and decreases in the eastern, southern, and central parts. The temporal and spatial variability of precipitation in the Altiplano region is influenced by the easterly moisture flux and the interaction between the El Niño Southern Oscillation (ENSO) and below-average values. The study utilizes water level data for Lake Titicaca and IPO data from 1914 to 2015. The analysis employs wavelet transform and empirical orthogonal function (EOF) techniques to identify the relationship between water levels and IPO. The results indicate multidecadal variability in water levels associated with El Niño/La Niña events and the IPO. The negative phase of the IPO aligns with extreme drought periods, suggesting a connection between the IPO climate index and drought events. The EOF analysis shows a moderate positive correlation between water levels and IPO. The findings highlight the importance of considering IPO and its interaction with ENSO in understanding drought patterns in the Altiplano region. However, other atmospheric conditions also influence precipitation in the region. The study contributes to a better understanding of the factors affecting water levels and droughts in the Peruvian Altiplano, with implications for water resource management in the region.

Research on water level forecasting and hydraulic parameter calibration in the 1D open channel hydrodynamic model using data assimilation

Data assimilation (DA) is an essential technique for improving the accuracy of state prediction in numerical simulation models. To enhance the effectiveness of DA in state estimation, the state-parameter joint data assimilation strategy has been proposed. However, limited attention has been given to the impact of state-parameter estimation Ensemble Kalman Filter (EnKF) on multi-parameter calibration in hydrodynamic models. In this paper, aiming at meeting the state correction and multi-parameter calibration requirements in a water delivery system under gate control, a state-parameter estimation EnKF framework and a model error setting strategy in the EnKF is proposed. The proposed method is applied to both a synthetic and a real-world open channel water delivery system and compared with the state estimation EnKF and the state-parameter estimation EnKF without model errors. The results demonstrate that the state-parameter estimation EnKF achieves better water level assimilation and forecasting performance than the state estimation EnKF, and that incorporating model errors into the assimilation significantly improves the water level estimation and parameter calibration. Furthermore, adding model error to the state variables other than water level or flow variables can further enhance the water level forecasting accuracy. This study provides valuable insights for guiding the state-parameter assimilation in open channel hydrodynamic models and realizing the state perception of open channel water delivery systems.

Flood vulnerability under sea level rise for a coastal community located in a backbarrier environment, Portugal

Sea level rise will be a major threat to coastal communities within the next century due to the intensity and severity of the floods it can cause. A new methodology considering water infiltration, slope, and hydraulic connectivity was developed to assess the potential inundation extension associated with different total water level and sea level rise scenarios on sandy coasts. This methodology was applied for the current conditions as well as 2050 and 2100 scenarios of storm surge and high tide levels with return periods of 1 year and 100 years. The study area is Culatra village, located on the lagoon side of a barrier island in southern Portugal. The effects of shoreline evolution after the construction of a harbor and associated beach nourishment were also evaluated within the inundation scenarios. The results show that, within the study area, total water level variations caused by sea level rise have a greater influence on the inundation extension than shoreline retreat. The village appears to be safe for the current and 2050 total water level scenarios with a 1-year return period but would be highly affected by 100-year return periods, especially from 2050 onwards. This novel approach represents an improvement on more common flood mapping methods such as the bathtub approach and can be easily applied to other backbarrier environments under sea level rise or facing coastal erosion.

Trend Analysis of Groundwater Levels in Kalpathypuzha Sub-Basin of Bharathapuzha, Kerala in India

Groundwater is one of the most precious and significant sources of water in the world. The understanding of groundwater level variability and trend is crucial for water resources planning in a region. The present study was conducted in the Kalpathypuzha sub-basin of Bharathapuzha. The variability of ground water levels was analyzed using various descriptive statistics such as mean, standard deviation, coefficient of variation, skewness and kurtosis. The groundwater level trend was estimated using the Mann-Kendall test and Sen’s slope estimator. Twelve observation wells evenly distributed in the blocks of Kuzhalmannam, Palakkad, Malampuzha and Chittur blocks of Palakkad districts in Kerala were selected for the study. The results of variability analysis showed that, the highest mean monthly groundwater level of 139.1 m was found for the well 139 of Chittur block in September and the lowest mean monthly groundwater level of 61.5 m was found for the well 129 of Palakkad block in September. The highest mean annual groundwater level was 138.9 m in the year 2007 for the well 139 of Chittur block and the lowest was 62.1 m in the year 2016 for the well 129 of Palakkad block. The results of trend analysis showed a decreasing pre-monsoon groundwater level trend in three wells viz. well 129 of Palakkad block and wells 133 and 142 of Malampuzha block while decreasing post-monsoon groundwater level trend was observed in well 139 of Chittur block. There was no significant trend in the rest of the wells for both the pre-monsoon and post-monsoon periods.

A data-driven approach to predict hydrometeorological variability and fluctuations in lake water levels

A data-driven approach to predict hydrometeorological variability and fluctuations in lake water levels

Assessment of Spatial Variability of Groundwater Levels in Moroto District, Uganda

Globally, the variation of groundwater levels is increasingly overwhelming due to over exploitation resulting from population growth. The dynamic nature of socio-economic activities in Moroto District such as agriculture, settlements and increased trends in irrigation technology has been well-known worldwide as common parameters triggering groundwater variability. Nevertheless, determination of groundwater levels for groundwater management and development purpose is a challenge due to spatial variability in levels across Moroto District. In this study, geostatistical technique in Geographical Information System (GIS) was used to analyze spatial variability of water levels in the study area. The analysis utilized ordinary Kriging method to predict the spatial variation of groundwater levels for 189 measured boreholes. The resultant groundwater level variation map generated using Gaussian model depicts change in groundwater levels varying significantly across the study area dropping by 12 m to 50 m. Significant variations of groundwater levels were observed in the western, central and south eastern part of the study area which are highly populated areas and therefore, the potential of overexploitation. Generated map can be used as first-hand information for decision makers and water managers in management of groundwater resources in Moroto District.

Variations in Aquatic Vegetation Diversity Responses to Water Level Sequences during Drought in Lakes under Uncertain Conditions

Water level variability and temporal change are critical for shaping the structure of aquatic vegetation. Much research has examined the response of aquatic vegetation to hydrological metrics. However, the hydrological sequence is a fundamental driver of aquatic ecosystem structure and function. Given the aleatory uncertainty of future water levels under an unstable climate, how aquatic vegetation responds to changing dynamics in hydrological processes, especially shifting water level sequences, remains insufficiently explored. In this paper, we establish an evaluation framework to study the response of vegetation diversity to variation in water level sequences during a drought event. To do this, the uncertainty and variability of water level processes are both considered. Altering water level processes was achieved using two types of scenarios in order to explore the effects of differing water level sequences (i.e., changing the order of high vs. low water levels) on the probability distribution of four indexes of aquatic plant diversity (e.g., Margalef’s, Simpson’s, Shannon’s, and Pielou’s evenness index). Our results show that altering the order of water level state can lead to differences in the diversity of aquatic vegetation, with a pronounced impact on vegetation complexity. This suggests that the specific sequence of water level events is critical for shaping aquatic vegetation structure. In addition, we found that a uniform distribution of water level state is beneficial for enhancing a species’ dominance in aquatic vegetation. Our findings provide guidance for improving the future development of freshwater ecosystem protection and lake management.

Unsupervised Domain Adaptation Damage Identification Approach of High Arch Dams after Earthquakes

In actual concrete arch dam engineering scenarios, the dynamic data obtained by the health monitoring system of an arch dam are incomplete. The data acquired typically depend on the state of the dam structure, that is, whether it is intact or incomplete. Besides, the future environmental loads of the structure are unpredictable. Thus, environmental noise is also uncertain. In practical engineering, the use of a damage identification model constructed based on incomplete information is problematic in scenarios with variable loads. Consequently, detecting the water level in actual arch dam projects after an earthquake and determining the impact of environmental uncertainty are necessary. Accordingly, this paper proposes a denoising contractive sparse deep autoencoder (DCS-DAE) model based on domain adaptation. The core idea of the proposed method is to constrain the data probability distribution of feature spaces in the source and target domains using maximum mean discrepancy. This fusion enables the DCS-DAE model to be capable of feature extraction. Moreover, it resolves the problem in which the objective function cannot be applied to other similar scenarios because of the lack of consistency constraints of feature spaces in the source and target domains. Four working conditions are designed to reproduce the uncertainty of structural modeling and the variability of water levels. The conditions are based on the postseismic water level detection requisites of dams in practical engineering. The results show that the proposed anomaly detection model enhances the generalization performance of the DCS-DAE in terms of feature design. Hence, the constructed model can “infer other things from one fact.” The results of this study are meaningful for the real-time cross-domain monitoring of structures under variable load conditions, providing a driving force to apply similar methods to practical arch dam projects.

Response mechanism of groundwater dynamics to Freeze–thaw process in seasonally frozen soil areas: A comprehensive analysis from site to regional scale

Studying the dynamic mechanism of water-level variations during the freeze–thaw period in seasonally frozen soil regions is an important premise and foundation for winter agricultural irrigation and groundwater resource assessment. Freezing and thawing-induced groundwater-level variations have been observed in regions with a shallow water table depth. However, whether the groundwater level is affected by the freeze–thaw process and the extent of this effect should be verified and discussed on a wider spatiotemporal scale. To this end, this study selected the plain area of Jilin Province, China as an example, and based on a comprehensive analysis of dynamic groundwater-level monitoring data from 114 monitoring wells, the distribution of the meteorological data and soil types and two typical experimental monitoring sites in the area, the dynamic characteristics and influencing factors of groundwater-level variations during the freeze–thaw period were identified. Combined with a multi-factor statistical analysis of the monitoring data at the regional scale of the plain area of Jilin Province, China, the response mechanism of the groundwater level to the freeze–thaw process in the seasonally frozen plain area was summarized. The results showed that: (1) The dynamic phenomenon where the groundwater level falls in the freezing period and rises in the thawing period due to the freeze–thaw process was widespread in seasonally frozen soil regions; (2) The depth threshold of the groundwater level affected by the freeze–thaw process was the sum of the maximum frozen soil depth and the maximum capillary rise height; (3) The main factors controlling the groundwater-level variation during the freeze–thaw period were the initial water-level depth and the maximum snow cover thickness; based on a random forest model, the groundwater-level variation during the freeze–thaw process could be accurately calculated with these main controlling factors; (4) The groundwater-level dynamics during the freeze–thaw process was mainly controlled by the exchange of water between the groundwater and the vadose zone system, and the rise in the water level was only partially replenished by the snowmelt water. The research results have an important guiding significance for winter agricultural irrigation and groundwater recharge resource evaluation.

Comparative characterization of sandstone microstructure affected by cyclic wetting-drying process

As a consequence of seasonal variations in groundwater level and reservoir water level, natural rocks generally experience the cyclic wetting-drying process, in which the change in microstructure becomes a critical factor leading to the deterioration of the macro-physical and mechanical properties of rocks. However, it remains a great challenge to quantitatively characterize the microstructures of rock, especially during the wetting-drying process. In this study, a systematic experimental investigation involving multiple techniques (mercury injection capillary pressure (MICP), computer tomography (CT), scanning electron microscope (SEM), and pores (particles) and cracks analysis system (PCAS) software package-based image analysis) were conducted to study the microstructure of sandstone subjected to cyclic wetting-drying. The results show that sandstone experiences increasing microporosity during the cyclic wetting-drying process, with progressive changes in micro grains, defects, and micropore structure and morphology. The pore compositions gradually change into a bimodal distribution with dominating small-medium pores (10 nm-10 μm) and large pores (>10 μm). Eventually, connected crack networks and large-scale fractures develop. There is a strong correlation between the microporosity values evaluated by CT and MICP, indicating the capacity of describing the micropore compositions ranging from 0.03 to 0.78 mm. Besides, comparisons of the three techniques (i.e., MICP, CT, and SEM) and evolution mechanisms of sandstone microstructures are further discussed.

Novel Techniques to Study the Effect of Parapet Wall Geometry on the Performance of Piano Key Weirs

Piano key weirs (PKWs) with crown parapet walls effectively manage water levels and maximize storage. However, their efficiency is compromised by interactions between water flow and submerged outlets during rising water levels. This study investigates novel parapet wall designs to improve PKW performance and reduce submergence effects. The experiment focuses on a PKW with a fixed 12.6 cm weir height. Three parapet wall configurations are tested: Mode 1 (walls on all apex), Mode 2 (walls fixed on sides and inlet), and Mode 3 (walls along the sides). Each mode includes three parapet wall profiles: rectangular (consistent form), triangular, and trapezoidal (varying characteristics). Results indicate that parapet wall design significantly affects water level variations with increasing wall height. Mode 3, featuring triangular and trapezoidal parapet walls, demonstrates the highest discharge capacity among the examined profiles. The discharge coefficient correlates with parapet wall height and form. Notably, the triangular wall in Mode 3 outperforms Modes 1 and 2 when parapet walls maintain an R/P ratio of 0.36. This study introduces innovative parapet wall designs to enhance PKW efficiency. By implementing advanced configurations, significant improvements in water control and discharge capacity can be achieved. These findings contribute to the state-of-the-art in PKW technology and offer valuable insights for practical engineering applications.

Near real-time altimetry for river monitoring—a global assessment of Sentinel-3

For applications such as weather, flood, and drought forecasting that need water level estimates as soon as possible, near real-time (NRT) products are most appropriate. Unlike in-situ sensors for water level measurements, which typically deliver NRT data, satellite altimeters deliver physically meaningful observations with substantial delays after acquisition. The new radar altimetry mission, Sentinel-3, is capable of delivering NRT water levels within a few hours of observation. Currently, it remains unexplored how accurate the NRT product is in the context of river monitoring. This study assesses Sentinel-3A/B NRT products in mapping river water level variations globally. Based on a three-year comparison, we find that the water level derived from NRT is almost as good as that from the delayed products (median root-mean-square error (RMSE): 21.5 cm and 23.5 for S3A and S3B), and both products achieve very similar RMSE values (median: 52.5 cm and 59.0 cm for NRT and non-time critical) against in-situ data at 25 locations. This study highlights the usefulness of Sentinel-3 NRT product for river monitoring and forecasting. And we recommend the NRT product if latency is a primary concern.

Influence of water-level variability on fish assemblage and natural reproduction following connectivity enhancement in a Typha dominated coastal wetland, USA.

We evaluated a wetland habitat modification strategy to contrast fish assemblage structure and the production of young-of-the-year (YOY) fish between different engineered habitats (i.e., spawning pool complexes and connectivity channels) relative to unmodified lateral channels in a large drowned river mouth tributary of the St. Lawrence River. Prior to habitat modifications, the coastal wetland was impaired by water level regulations, dominance of invasive hybrid cattail, Typha x glauca, that collectively replaced or created barriers to seasonally flooded spawning habitats important to fish. Connectivity enhancements provided fish access along a wetland habitat gradient from sedge-meadows to the deeper water robust emergent main-channel. Across an eight-year fish emigration dataset (2012, 2013, 2016-2021) more than 90% of all captured fish (Ntotal = 218,086 fish) were YOY and modified habitats outperformed the unmodified channels in total fish catch-per-unit-effort (CPUE) per year (both YOY and non-YOY). Spawning pool complexes had higher YOY species richness than unmodified channel habitats. Fish assemblage structure differed between the modified habitats, where connectivity channels and unmodified channels shared a more similar fish assemblage than spawning pool complexes. Modified habitats, however, supported warmer water and higher dissolved oxygen than the unmodified channels. Redundancy analysis and linear mixed-effect modeling with abiotic variables (hydrology, temperature and dissolved oxygen) showed significant effects on fish assemblage structure, species richness and CPUE of fish emigrating from the modified and unmodified habitats. Historic flooding in 2017 and 2019 was a primary driver of YOY fish production and fish assemblage structure, but also appeared associated with near anoxic conditions systemwide. YOY fish for several species was inversely affected by floods at spawning pool complexes, however CPUE of YOY fish for these species appeared unaffected at the connectivity channels despite low dissolved oxygen. Diversified habitat structure (i.e., connectivity channels and spawning pool complexes) offers a management option to enhance habitat for fish that allowed compensatory effects on the capture of YOY fish of several species during floods. This multi-faceted outcome from the habitat modifications resulted in unique fish assemblages between the channelized and spawning pool habitat. A connectivity-based habitat enhancement strategy provides adaptability for an uncertain climatic and regulatory future for the Laurentian Great Lakes and St. Lawrence River.

Seasonal Reproductive Cycle of Wild Alligator Snapping Turtles (Macrochelys temminckii) in Southwest Georgia

We studied the reproductive cycle of wild Macrochelys temminckii (Alligator Snapping Turtle) in southwest Georgia from March 2008 to September 2010. We measured plasma testosterone (T), estradiol (E2), and corticosterone (C). Seasonal changes in T were observed in males, with maximum concentrations occurring in October. Evidence of mating and male combat were seen in April. Females displayed seasonal changes in T and E2 concentrations, with peaks occurring in March and April, respectively, (in association with mating and ovulation) and again in September and October, respectively, (in association with follicular development and vitellogenesis). We observed oviductal eggs (mean clutch size = 28.5) in April. Concentrations of C were not significantly different between months. Reproductive patterns coincided with seasonal variation in temperature and water level.

Mapping South Florida Daily Fire Risk for Decision Support Using Fuel Type, Water Levels, and Burn History

Mapping fire risk in South Florida depends on spatially varying water levels, fuel characteristics, and topography. When surface water levels recede below the lowest topographic features (cypress strands, marshes, etc.), the ecosystem loses its natural, wetted fire breaks, and landscape-level fire risk increases. We developed a geospatial method to generate daily, categorical fire risk maps; the maps visualize low-to-high risk areas using a newly developed 100 m DEM, modeled water levels, fuel types, and fire management units. We assigned fire risk by creating a water level distribution for each unique combination of fuel type and fire management unit; fire risk was then assigned for each pixel based on risk percentiles commonly used by fire management agencies. Assigning risk based on unique fuel types and management units helped avoid over- or under-assigning fire risk that may occur when applying landscape-level “average” risk relationships. Daily maps also incorporated (1) energy release component data to better estimate fuel moisture and (2) historical burn footprints to reduce risk in recently burned areas. Our data-driven approach generated at management-relevant spatial scales may enable more informed prescribed burn planning and may increase the efficiency of staff and resource allocation across the landscape on high-wildfire-risk days.

Mapping Water Levels across a Region of the Cuvette Centrale Peatland Complex

Inundation dynamics are the primary control on greenhouse gas emissions from peatlands. Situated in the central Congo Basin, the Cuvette Centrale is the largest tropical peatland complex. However, our knowledge of the spatial and temporal variations in its water levels is limited. By addressing this gap, we can quantify the relationship between the Cuvette Centrale’s water levels and greenhouse gas emissions, and further provide a baseline from which deviations caused by climate or land-use change can be observed, and their impacts understood. We present here a novel approach that combines satellite-derived rainfall, evapotranspiration and L-band Synthetic Aperture Radar (SAR) data to estimate spatial and temporal changes in water level across a sub-region of the Cuvette Centrale. Our key outputs are a map showing the spatial distribution of rainfed and flood-prone locations and a daily, 100 m resolution map of peatland water levels. This map is validated using satellite altimetry data and in situ water table data from water loggers. We determine that 50% of peatlands within our study area are largely rainfed, and a further 22.5% are somewhat rainfed, receiving hydrological input mostly from rainfall (directly and via surface/sub-surface inputs in sloped areas). The remaining 27.5% of peatlands are mainly situated in riverine floodplain areas to the east of the Congo River and between the Ubangui and Congo rivers. The mean amplitude of the water level across our study area and over a 20-month period is 22.8 ± 10.1 cm to 1 standard deviation. Maximum temporal variations in water levels occur in the riverine floodplain areas and in the inter-fluvial region between the Ubangui and Congo rivers. Our results show that spatial and temporal changes in water levels can be successfully mapped over tropical peatlands using the pattern of net water input (rainfall minus evapotranspiration, not accounting for run-off) and L-band SAR data.