Stepwise Adaptation Research Articles

Two hundred and twenty-nine cases of bidirectional cavopulmonary anastomosis with and without antegrade pulmonary blood flow, a single-center experience.

Bidirectional cavopulmonary anastomosis is palliative surgical procedure for stepwise adaptation of the ventricle by time-phased relief of blood volume from the single functional ventricle. There still exists a controversial question regarding maintaining additional antegrade pulmonary blood flow. We retrospectively reviewed the surgical cases of 261 patients who underwent bidirectional cavopulmonary anastomosis in our institution from 2012 to 2022 with special regard to antegrade pulmonary blood flow as our preferred strategy. The mean age at the time of surgery was 33.1 months (range 2.9-192 months), and the mean weight was - 7.6 kg (range 3.9-38 kg). Furthermore, we divided all the patients into two groups: in group 1 (n = 182) - patients who underwent bidirectional cavopulmonary anastomosis with antegrade pulmonary blood flow, and in group 2 (n = 47) - patients without antegrade pulmonary blood flow. The mean follow-up time was 56 months (range 24-120 months). Mortality rate was 4.8 % (n = 11) in the past 10 years. Statistical difference between groups was in the following positions: group 2 had less ICU stay (p < 0.000125) and hospital stay (p < 0.017110); group 1 had a longer duration of pleural effusion (p < 0.000003) and amount of drainage output (p < 0.007), also demonstrated higher oxygen saturation (p < 0.000264) and Glenn shunt pressure (p < 0.002) after the surgery; but there was no difference in oxygen saturation after 6, 12, and 24 months; mortality in both groups has no statistic difference. Considering our experience, we take a stand on the controlled to antegrade pulmonary blood flow strategy during bidirectional cavopulmonary anastomosis.

A Step-Wise Domain Adaptation Detection Transformer for Object Detection under Poor Visibility Conditions

A Step-Wise Domain Adaptation Detection Transformer for Object Detection under Poor Visibility Conditions

The necessity of pragmatic muddling. Ten Swedish early adopter cities navigating climate adaptation policy-implementation in the urban built environment

While climate adaptation planning and implementation is gradually increasing across the globe, there is a documented gap between what is done and what needs to be done. Researchers have documented climate adaptation efforts at the strategic policy-making level and in urban planning practices, but less is known about how cities navigate the intricacies of climate adaptation policy-progression in the existing built environment. Contributing to the analytical unpacking of how to reduce policy implementation gaps, this paper targets ten Swedish early adopter cities seeking to proactively and pragmatically progress with their climate adaptation efforts from policy-formation to implementation in the urban built environment. Qualitative analyses of interviews and policy-documents illustrate that the cities, despite their early adopter status, struggle with stepwise policy-progression and get stuck when approaching implementation. Ensuring appropriate climate adaptation in the existing urban built environment becomes problematic due to current legal distribution of responsibilities, diverse land-ownership patterns and path-dependent structures and configurations within cities that are dense, intricate and tightly developed over of time. We identify three pragmatic action-strategies adopted to create solution space and allowing the cities to proceed: event-driven, target-driven and opportunity-driven climate adaptation, each having their advantages and disadvantages for ensuring urban robustness, as well as different requirements for up-scaling. The analysis enables important lessons of climate adaptation policy-progression, the promise and pitfalls of stepwise adaptation and the necessity of pragmatic muddling that is required to make climate adaptation work in the existing urban built environment.

Effects of adaptive duration to salinity in drinking water on behavior, weight gain and blood biochemical parameters in growing goats.

This experiment aimed to determine the effect of adaptive duration to saline water on behaviors, weight gain and blood biochemical parameters in growing goats. The experiment was arranged in a completely randomized design, which included four treatments with five animals per group. The goats were administered either fresh water (control) or seawater with a salinity of 1.5%, with varying durations of adaptation to seawater. The adaptive durations included an abrupt change (A0) from fresh water to seawater with a salinity of 1.5% or stepwise adaptation either 4 (A4) or 7 (A7) days of increasing saline concentrations. The results showed that dry matter intake in the non-adapted goats (A0 group) was lower than that of the control group or the adapted goats throughout the experiment (p<0.05). In contrast, water intake from drinking saline water was greater than that in the control group (p<0.05). Body weigh did not differ among the treatments; however, non-adapted goats exhibited a lower weight gain than the adapted goats (p<0.05). The goats in the A0 and A4 groups exhibited increased plasma levels of urea, AST, and ALT compared with the control and A7 groups. However, blood electrolyte levels remained unchanged and were within the normal range for goats. Therefore, it is concluded that the stepwise adaptation to seawater with a salinity of 1.5% for 21 days has no influence on productivity and health status of goats.

Meralgia Paresthetica-An Approach Specific Neurological Complication in Patients Undergoing DAA Total Hip Replacement: Anatomical and Clinical Considerations.

Introduction: Mini-invasive surgical (MIS) approaches to total hip replacement (THR) are becoming more popular and increasingly adapted into practice. THR via the direct anterior approach (MIS DAA) has become a rather controversial topic in hip arthroplasty literature in the last decades. Our retrospective observational study focuses on the prevalence of one approach-specific complication-lateral femoral cutaneous nerve (LFCN) iatrogenic lesion-and tries to clarify the possible pathogenesis of this injury. Methods: This is a retrospective single-cohort observational single-center and single-surgeon study. Our patient records were searched for the period from 2015 to 2017-after a safe period of time after the learning curve for MIS DAA. All intra- and post-operative lesions of the LFCN were recorded. Lesion of the LFCN was confirmed by a neurological examination. Minimum patient follow-up was 2 years. Results: This study involved 417 patients undergoing single-side THR via MIS DAA. Patients were examined on follow-up visits at 6 weeks, 6 months, 1 year, and 2 years after surgery. There were 17 cases of LCFN injury at the 6 weeks early follow-up visit (4.1%). All cases of clinically presenting LFCN injury resolved at the 2-year follow-up ad integrum. Discussion: Possible explanations of such neurological complications are direct iatrogenic injury, vigorous traction, hyperextension, or extreme external rotation of the operated limb. Use of a traction table or concomitant spinal pathology and deformity also play a role. Prevention involves stepwise adaptation of the approach during the learning curve period by attending cadaver lab courses, rational use of traction and hyperextension, and careful surgical technique in the superficial and deep fascial layers. Dynamometers could be used to visualise the limits of manipulation of the operated limb. Conclusions: Neurological complications are not as rare but questionably significant in patients undergoing THR via the DAA. Incidental finding of LFCN injury has no effect on the functional outcome of the artificial joint. It can lead to lower subjective satisfaction of patients with the operation, which can be avoided with careful education and management of expectations of the patients.

Loss of Key EMT-Regulating miRNAs Highlight the Role of ZEB1 in EGFR Tyrosine Kinase Inhibitor-Resistant NSCLC.

Despite recent advances in the treatment of non-small cell lung cancer (NSCLC), acquired drug resistance to targeted therapy remains a major obstacle. Epithelial-mesenchymal transition (EMT) has been identified as a key resistance mechanism in NSCLC. Here, we investigated the mechanistic role of key EMT-regulating small non-coding microRNAs (miRNAs) in sublines of the NSCLC cell line HCC4006 adapted to afatinib, erlotinib, gefitinib, or osimertinib. The most differentially expressed miRNAs derived from extracellular vesicles were associated with EMT, and their predicted target ZEB1 was significantly overexpressed in all resistant cell lines. Transfection of a miR-205-5p mimic partially reversed EMT by inhibiting ZEB1, restoring CDH1 expression, and inhibiting migration in erlotinib-resistant cells. Gene expression of EMT-markers, transcription factors, and miRNAs were correlated during stepwise osimertinib adaptation of HCC4006 cells. Temporally relieving cells of osimertinib reversed transition trends, suggesting that the implementation of treatment pauses could provide prolonged benefits for patients. Our results provide new insights into the contribution of miRNAs to drug-resistant NSCLC harboring EGFR-activating mutations and highlight their role as potential biomarkers and therapeutic targets.

Sequential intrahost evolution and onward transmission of SARS-CoV-2 variants

Persistent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have been reported in immune-compromised individuals and people undergoing immune-modulatory treatments. Although intrahost evolution has been documented, direct evidence of subsequent transmission and continued stepwise adaptation is lacking. Here we describe sequential persistent SARS-CoV-2 infections in three individuals that led to the emergence, forward transmission, and continued evolution of a new Omicron sublineage, BA.1.23, over an eight-month period. The initially transmitted BA.1.23 variant encoded seven additional amino acid substitutions within the spike protein (E96D, R346T, L455W, K458M, A484V, H681R, A688V), and displayed substantial resistance to neutralization by sera from boosted and/or Omicron BA.1-infected study participants. Subsequent continued BA.1.23 replication resulted in additional substitutions in the spike protein (S254F, N448S, F456L, M458K, F981L, S982L) as well as in five other virus proteins. Our findings demonstrate not only that the Omicron BA.1 lineage can diverge further from its already exceptionally mutated genome but also that patients with persistent infections can transmit these viral variants. Thus, there is, an urgent need to implement strategies to prevent prolonged SARS-CoV-2 replication and to limit the spread of newly emerging, neutralization-resistant variants in vulnerable patients.

Apoptotic gene loss in Cnidaria is associated with transition to parasitism

The phylum Cnidaria consists of several morphologically diverse classes including Anthozoa, Cubozoa, Hydrozoa, Polypodiozoa, Scyphozoa, Staurozoa, and Myxozoa. Myxozoa comprises two subclasses of obligate parasites—Myxosporea and Malacosporea, which demonstrate various degrees of simplification. Myxosporea were previously reported to lack the majority of core protein domains of apoptotic proteins including caspases, Bcl-2, and APAF-1 homologs. Other sequenced Cnidaria, including the parasite Polypodium hydriforme from Polypodiozoa do not share this genetic feature. Whether this loss of core apoptotic proteins is unique to Myxosporea or also present in its sister subclass Malacosporea was not previously investigated. We show that the presence of core apoptotic proteins gradually diminishes from free-living Cnidaria to Polypodium to Malacosporea to Myxosporea. This observation does not favor the hypothesis of catastrophic simplification of Myxosporea at the genetic level, but rather supports a stepwise adaptation to parasitism that likely started from early parasitic ancestors that gave rise to Myxozoa.

CLONAL MICROPROPAGATION OF PAULOWNIA IN VITRO

The purpose of the article – to develop technological methods of clonal micropropagation of paulownia in vitro. Methods. Paulownia plants Paulownia Sieb. et Zucc. were the material for the research. In the course of research, generally accepted methods in plant biotechnology were used. Aseptic work was performed in the laminar box KPG-1. Murashige and Skuga (MS) were used as the basic nutrient medium for the cultivation of isolated buds and micropods. The results. The method of clonal micropropagation based on the culture of isolated apical meristems provides a high reproduction rate, maximum genetic stability and recovery of the resulting regenerating plants. The most effective scheme of sterilization of paulownia is stepwise treatment of plant material with 70% ethanol solution and 1% sodium hypochlorite solution. The yield of sterile explants was 92.5–95.0%, viability – 90.0–97.5%. At the stage of introduction into in vitro culture, the optimal nutrient medium is MS, supplemented with kinetin 1.0 mg/l and GA 0.5 mg/l, at which the reproduction rate was the highest and was 8.7–9.2. At the stage of proper micropropagation, the most intensive proliferation of shoots also occurred on the nutrient medium MS, supplemented with kinetin 1.0 mg/l and GA 0.5 mg/l, which provided the highest reproduction rate – 10.3–12.0. At the stage of rooting of micro-shoots the most optimal was the nutrient medium 1/2 MS, supplemented with a IBА of 0.5 mg/l, at which the frequency of rhizogenesis was 95.0% and formed 5.3–7.8 roots with a length of 78.5–95.2 mm. Stepwise adaptation of plants to in vivo conditions for 40 days in climatic chambers and growing in a greenhouse ensured the yield of seedlings at the level of 85.0–95.0%. Conclusions. On the basis of the carried-out experimental researches methods of clonal micropropagation paulownia in vitro, which are expedient to use for mass production of genetically homogeneous healthy planting material.

Creative destruction: New protein folds from old

Mechanisms of emergence and divergence of protein folds pose central questions in biological sciences. Incremental mutation and stepwise adaptation explain relationships between topologically similar protein folds. However, the universe of folds is diverse and riotous, suggesting more potent and creative forces are at play. Sequence and structure similarity are observed between distinct folds, indicating that proteins with distinct folds may share common ancestry. We found evidence of common ancestry between three distinct β-barrel folds: Scr kinase family homology (SH3), oligonucleotide/oligosaccharide-binding (OB), and cradle loop barrel (CLB). The data suggest a mechanism of fold evolution that interconverts SH3, OB, and CLB. This mechanism, which we call creative destruction, can be generalized to explain many examples of fold evolution including circular permutation. In creative destruction, an open reading frame duplicates or otherwise merges with another to produce a fused polypeptide. A merger forces two ancestral domains into a new sequence and spatial context. The fused polypeptide can explore folding landscapes that are inaccessible to either of the independent ancestral domains. However, the folding landscapes of the fused polypeptide are not fully independent of those of the ancestral domains. Creative destruction is thus partially conservative; a daughter fold inherits some motifs from ancestral folds. After merger and refolding, adaptive processes such as mutation and loss of extraneous segments optimize the new daughter fold. This model has application in disease states characterized by genetic instability. Fused proteins observed in cancer cells are likely to experience remodeled folding landscapes and realize altered folds, conferring new or altered functions.

Stepwise Domain Adaptation (SDA) for Object Detection in Autonomous Vehicles Using an Adaptive CenterNet

In recent years, deep learning technologies for object detection have made great progress and have powered the emergence of state-of-the-art models to address object detection problems. Since the domain shift can make detectors unstable or even crash, the detection of cross-domain becomes very important for the design of object detectors. However, traditional deep learning technologies for object detection always rely on a large amount of reliable ground-truth labelling that is laborious, costly, and time-consuming. Although an advanced approach CycleGAN has been proposed for cross-domain object detection tasks, the ability of CycleGAN to reduce the divergence across domains at the feature level is limited. In this paper, a stepwise domain adaptation (SDA) detection method is proposed to further improve the performance of CycleGAN by minimizing the divergence in cross-domain object detection tasks. Specifically, the domain shift is addressed in two steps. In the first step, to bridge the domain gap, an unpaired image-to-image translator is trained to construct a fake target domain by translating the source images to the similar ones in the target domain. In the second step, to further minimize divergence across domains, an adaptive CenterNet is designed to align distributions at the feature level in an adversarial learning manner. Our proposed method is evaluated in domain shift scenarios based on the driving datasets including Cityscapes, Foggy Cityscapes, SIM10k, and BDD100K. The results show that our method is superior to the state-of-the-art methods and is effective for object detection in domain shift scenarios.

Heterotrophic bio-reduction process of hexavalent chromium: Toxic effects, concentration-adaptation and sustainable sludge-based bio-augmentation strategy

For high hexavalent chromium (Cr(VI)) industrial wastewater, heterotrophic bio-reduction is a promising process. Nevertheless, a high concentration of Cr(VI) (e.g., more than 100 mg L−1) may still devastate the sustainability of the bioprocess. In this paper, the Cr(VI) toxic effects and resistance on concentration-adaptation and a sludge-based bio-augmentation were studied. The results suggested: 1) The Cr(VI) exposure took 6–24 h to cause significantly the toxic inhibition and lethal effects on the sludge communities. 2) Although adaptation to 50 mg L−1 influent Cr(VI) improved Cr(VI) reduction by 2 times, the stepwise adaptation was ineffective for 100 mg L−1 Cr(VI). Lowering the Cr(VI) loading could not recover the dysfunctional sludge. 3) A bio-augmentation strategy by exchanging Cr(VI) stressed sludge with Cr(VI) free sludge at intervals (e.g., 0.8 gMLVSS L−1 every 3.5 d) was proposed and treated successfully 100 mg L−1 Cr(VI). The mechanism behind might be that exchanging sludge at intervals maintained a relatively high Cr(VI) reduction bacteria activity and a stable live/dead bacteria ratio. 4) The variation of Cr(VI) reductase distribution, morphology and microbial community during the concentration-adaption and bio-augmentation implied the sludge might use multiple toxic resistance mechanisms such as sludge aggregation, the enrichment of Cr(VI) reduction bacteria. Therefore, through comprehensively testing, this work not only revealed the draws of concentration-adaptation for Cr(VI), but also developed a sustainable, convenient and robust sludge-based bio-augmentation strategy to overcome the highly toxic Cr(VI) wastewater.

Adaptation of the Oxygen Sensing System during Lung Development.

During gestation, the most drastic change in oxygen supply occurs with the onset of ventilation after birth. As the too early exposure of premature infants to high arterial oxygen pressure leads to characteristic diseases, we studied the adaptation of the oxygen sensing system and its targets, the hypoxia-inducible factor- (HIF-) regulated genes (HRGs) in the developing lung. We draw a detailed picture of the oxygen sensing system by integrating information from qPCR, immunoblotting, in situ hybridization, and single-cell RNA sequencing data in ex vivo and in vivo models. HIF1α protein was completely destabilized with the onset of pulmonary ventilation, but did not coincide with expression changes in bona fide HRGs. We observed a modified composition of the HIF-PHD system from intrauterine to neonatal phases: Phd3 was significantly decreased, while Hif2a showed a strong increase and the Hif3a isoform Ipas exclusively peaked at P0. Colocalization studies point to the Hif1a-Phd1 axis as the main regulator of the HIF-PHD system in mouse lung development, complemented by the Hif3a-Phd3 axis during gestation. Hif3a isoform expression showed a stepwise adaptation during the periods of saccular and alveolar differentiation. With a strong hypoxic stimulus, lung ex vivo organ cultures displayed a functioning HIF system at every developmental stage. Approaches with systemic hypoxia or roxadustat treatment revealed only a limited in vivo response of HRGs. Understanding the interplay of the oxygen sensing system components during the transition from saccular to alveolar phases of lung development might help to counteract prematurity-associated diseases like bronchopulmonary dysplasia.

Stepwise Stochastic Dictionary Adaptation Improves Microstructure Reconstruction with Orientation Distribution Function Fingerprinting.

Fitting of the multicompartment biophysical model of white matter is an ill-posed optimization problem. One approach to make it computationally tractable is through Orientation Distribution Function (ODF) Fingerprinting. However, the accuracy of this method relies solely on ODF dictionary generation mechanisms which either sample the microstructure parameters on a multidimensional grid or draw them randomly with a uniform distribution. In this paper, we propose a stepwise stochastic adaptation mechanism to generate ODF dictionaries tailored specifically to the diffusion-weighted images in hand. The results we obtained on a diffusion phantom and in vivo human brain images show that our reconstructed diffusivities are less noisy and the separation of a free water fraction is more pronounced than for the prior (uniform) distribution of ODF dictionaries.

Ancestral sequence reconstruction pinpoints adaptations that enable avian influenza virus transmission in pigs.

Understanding the evolutionary adaptations that enable avian influenza viruses to transmit in mammalian hosts could allow better detection of zoonotic viruses with pandemic potential. We applied ancestral sequence reconstruction to gain viruses representing different adaptive stages of the European avian-like (EA) H1N1 swine influenza virus as it transitioned from avian to swine hosts since 1979. Ancestral viruses representing the avian-like precursor virus and EA swine viruses from 1979–1983, 1984–1987, and 1988–1992 were reconstructed and characterized. Glycan array analyses showed stepwise changes in the hemagglutinin receptor binding specificity from recognizing both alpha2,3- and alpha2,6-sialosides to alpha2,6-sialosides; however, efficient transmission in piglets was enabled by adaptive changes in the viral polymerase protein and nucleoprotein that have been fixed after 1983. PB1-Q621R and NP-R351K increased viral replication and transmission in piglets when introduced into the 1979–1983 ancestral virus that lacked efficient transmissibility. The stepwise adaptation of an avian influenza virus to a mammalian host suggests that there may be opportunities to intervene and prevent interspecies jump through strategic coordination of surveillance and risk assessment activities.

Preadaptation of cell numbers for wound healing assays

Abstract In vitro wound healing assays are a suitable application to verify the efficiency of pharmaceuticals or growth factors that will be incorporated in or immobilized to e.g. electrospun biomaterials for wound dressings or other biological devices in advance. Thereby, various factors like culture conditions or cell density influence the specific cell proliferation. Hence, to establish a wound healing assay for various cell types, a stepwise adaptation of cell numbers was done for better estimation and comparison of cell density for the validation of the influence of drugs on the wound healing process. Cell proliferation of different tissue relevant cell types was evaluated by impedance measurements and live cell imaging. Cell numbers could be successfully adapted for assay specific cell densities. In general, a universal comparison of biological or chemical materials and agents in vitro may require the creation of appropriate ISO or OECD standards for a consistent and cell specific adaptation or demand of initial cell density.

Evaluation of PAO adaptability to oxygen concentration change: Development of stable EBPR under stepwise low-aeration adaptation

Recent research has shown the adaptability of Biological Nutrient Removal (BNR) systems to very low level dissolved oxygen (DO) concentration, mainly focusing in the nitrification ability that maintains the nitrogen oxidation process even at very low DO levels. Although step-wise aeration decrease on Enhanced Biological Phosphorus Removal (EBPR) is not fully comprehended. This study investigated the effect of reaching micro-aeration with adaptation strategies on EBPR performance. A step-wise oxygen concentration decrease, arriving at an average aeration level of 0.4 mgO2/L was evaluated, with an outcome of approximately 90 % phosphorus removal efficiency. Compared with different aeration modes, the highest phosphorus (P)-removal efficiency, P-release and lowest effluent phosphorus was achieved in gradual DO decrease strategy. On the other hand, an instant decrease in aeration from stable EBPR process from 2 mgO2/L to 0.4 mgO2/L adversely impacted P-removal by decreasing the efficiency to average 60 % and deteriorating the phosphorus removing microbial consortium. Comparison of results between instant and gradual DO-decrease, indicated the sensitivity of microorganisms to aeration. Microbial adaptation to decreased oxygen availability is crucial to reach high process performance. This study proposes, a potential aeration mode, which contributes in reduction of energy consumption in BNR systems through wastewater treatment.

Fed-batch production assessment of a tetravalent bispecific antibody: A case study on piggyBac stably transfected HEK293 cells

The transition from preclinical biological drug development into clinical trials requires an efficient upscaling process. In this context, bispecific antibody drugs are particularly challenging due to their propensity to form aggregates and generally produce low titers. Here, the upscaling process for a tetravalent bispecific antibody expressed by a piggyBac transposon-mediated stable HEK293 cell pool has been evaluated. The project was performed as a case study at Testa Center, a non-GMP facility for scale-up testing of biologics in Sweden, and encompassed media adaptation strategies, fed-batch optimization and a novel antibody purification technology. The cell pool was adapted to different culture media for evaluation in terms of cell viability and titers compared to its original Expi293 Expression Medium. These parameters were assessed in both sequential stepwise adaption and direct media exchanges. By this, a more affordable medium was identified that did not require stepwise adaptation and with similar titers and viability as in the Expi293 Expression Medium. Fed-batch optimizations resulted in culture densities reaching up to 20 × 106 viable cells/mL with over 90 % viability 12 days post-inoculum, and antibody titers three times higher than corresponding batch cultures. By implementing a novel high-speed protein A fiber technology (Fibro PrismA) with a capture residence time of only 7.5 s, 8 L of supernatant could be purified in 4.5 h without compromising the purity, structural integrity and function of the bispecific antibody. Results from this study related to medium adaptation and design of fed-batch protocols will be highly beneficial during the forthcoming scale-up of this therapeutic antibody.

Adaptation of Campylobacter field isolates to propionic acid and sorbic acid is associated with fitness costs

To reduce the burden of Campylobacter at different stages of the food chain, recent studies have shown the effectiveness of organic acids as a risk mitigation strategy. However, very little is known about possible adaptation responses of Campylobacter that lead to reduced susceptibility to organic acids. Here we investigated the adaptive responses of Campylobacter field isolates to organic acids and estimated the fitness costs. Exposure of two Campylobacter jejuni and one Campylobacter coli isolate to subinhibitory concentrations of propionic acid or sorbic acid resulted in twofold to fourfold increased minimal inhibitory concentration values for the adapted variants. With one exception, the decreased susceptibility was stable in at least 10 successive subcultures without selection pressure. Growth competition experiments revealed a reduced fitness of adapted variants compared to the wild-type isolates. A linear regression model allowed an estimation of the fitness cost. Growth kinetics experiments showed significantly prolonged lag phases in five of six adapted isolates while there was not a direct correlation in the maximum growth rates compared to the wild-type isolates. The results of the study showed that a stepwise adaptation of Campylobacter to organic acids is possible, but at the detriment of changes in growth behaviour and reduced fitness. The study contributes to the understanding of adaptive responses of Campylobacter to organic acids treatments, for example, as part of risk mitigation strategies.

Learning from satellite observations: increased understanding of catchment processes through stepwise model improvement

Abstract. Satellite observations can provide valuable information for a better understanding of hydrological processes and thus serve as valuable tools for model structure development and improvement. While model calibration and evaluation have in recent years started to make increasing use of spatial, mostly remotely sensed information, model structural development largely remains to rely on discharge observations at basin outlets only. Due to the ill-posed inverse nature and the related equifinality issues in the modelling process, this frequently results in poor representations of the spatio-temporal heterogeneity of system-internal processes, in particular for large river basins. The objective of this study is thus to explore the value of remotely sensed, gridded data to improve our understanding of the processes underlying this heterogeneity and, as a consequence, their quantitative representation in models through a stepwise adaptation of model structures and parameters. For this purpose, a distributed, process-based hydrological model was developed for the study region, the poorly gauged Luangwa River basin. As a first step, this benchmark model was calibrated to discharge data only and, in a post-calibration evaluation procedure, tested for its ability to simultaneously reproduce (1) the basin-average temporal dynamics of remotely sensed evaporation and total water storage anomalies and (2) their temporally averaged spatial patterns. This allowed for the diagnosis of model structural deficiencies in reproducing these temporal dynamics and spatial patterns. Subsequently, the model structure was adapted in a stepwise procedure, testing five additional alternative process hypotheses that could potentially better describe the observed dynamics and pattern. These included, on the one hand, the addition and testing of alternative formulations of groundwater upwelling into wetlands as a function of the water storage and, on the other hand, alternative spatial discretizations of the groundwater reservoir. Similar to the benchmark, each alternative model hypothesis was, in a next step, calibrated to discharge only and tested against its ability to reproduce the observed spatio-temporal pattern in evaporation and water storage anomalies. In a final step, all models were re-calibrated to discharge, evaporation and water storage anomalies simultaneously. The results indicated that (1) the benchmark model (Model A) could reproduce the time series of observed discharge, basin-average evaporation and total water storage reasonably well. In contrast, it poorly represented time series of evaporation in wetland-dominated areas as well as the spatial pattern of evaporation and total water storage. (2) Stepwise adjustment of the model structure (Models B–F) suggested that Model F, allowing for upwelling groundwater from a distributed representation of the groundwater reservoir and (3) simultaneously calibrating the model with respect to multiple variables, i.e. discharge, evaporation and total water storage anomalies, provided the best representation of all these variables with respect to their temporal dynamics and spatial patterns, except for the basin-average temporal dynamics in the total water storage anomalies. It was shown that satellite-based evaporation and total water storage anomaly data are not only valuable for multi-criteria calibration, but can also play an important role in improving our understanding of hydrological processes through the diagnosis of model deficiencies and stepwise model structural improvement.