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An increase in extreme precipitation is projected for many areas worldwide in the coming decades. To assess the impact of increased precipitation intensity on water security, we applied a regional-scale hydrological and soil erosion model, forced with regional climate model projections. We specifically considered the impact of climate change on the distribution of water between soil (green water) and surface water (blue water) compartments. We show that an increase in precipitation intensity leads to a redistribution of water within the catchment, where water storage in soil decreases and reservoir inflow increases. This affects plant water stress and the potential of rainfed versus irrigated agriculture, and increases dependency on reservoir storage, which is potentially threatened by increased soil erosion. This study demonstrates the crucial importance of accounting for the fact that increased precipitation intensity leads to water redistribution between green and blue water, increased soil erosion, and reduced water security. Ultimately, this has implications for design of climate change adaptation measures, which should aim to increase the water holding capacity of the soil (green water) and to maintain the storage capacity of reservoirs (blue water), benefiting rainfed and irrigated agriculture.

Worldwide, Mediterranean cropping systems face the complex challenge of producing enough high-quality food while preserving the quantity and quality of scarce water for people and agriculture in the context of climate change. While good management of nitrogen (N) is paramount to achieving this objective, the efficient strategies developed for temperate systems are often not adapted to the specificities of Mediterranean systems. In this work, we combine original data with a thorough literature review to highlight the most relevant drivers of N dynamics in these semi-arid systems. To do so, we provide an analysis at nested scales combining a bottom-up approach from the field scale, with a top-down approach considering the agro-food system where cropping systems are inserted. We analyze the structural changes in the agro-food systems affecting total N entering the territory, the contrasting response of yields to N availability under rainfed and irrigated conditions in a precipitation gradient, the interaction between N management and climate change adaptation, the main drivers affecting the release of Nr compounds (nitrate, ammonia, nitric oxide and nitrous oxide) compared with temperate systems and finally, the behavior of N once exported to highly regulated river networks. We conclude that sustainable N management in Mediterranean cropping systems requires the specific adaptation of practices to particular local agro-environmental characteristics with special emphasis on water availability for rainfed and irrigated systems. This approach should also include a systemic analysis of N input into the territory that is driven by the configuration of the agro-food system.

This research studies the effect of climate change on the hydrological behavior of two semi-arid basins. For this purpose, the Soil and Water Assessment Tool (SWAT) model was used with the simulation of two future climate change scenarios, one Representative Concentration Pathway moderate (RCP 4.5) and the other extreme (RCP 8.5). Three future periods were considered: close (2019–2040), medium (2041–2070), and distant (2071–2100). In addition, several climatic projections of the EURO-CORDEX model were selected, to which different bias correction methods were applied before incorporation into the SWAT model. The statistical indices for the monthly flow simulations showed a very good fit in the calibration and validation phases in the Upper Mula stream (NS = 0.79–0.87; PBIAS = −4.00–0.70%; RSR = 0.44–0.46) and the ephemeral Algeciras stream (NS = 0.78–0.82; PBIAS = −8.10–−8.20%; RSR = 0.4–0.42). Subsequently, the impact of climate change in both basins was evaluated by comparing future flows with those of the historical period. In the RCP 4.5 and RCP 8.5 scenarios, by the end of the 2071–2100 period, the flows of the Upper Mula stream and the ephemeral Algeciras stream will have decreased by between 46.3% and 52.4% and between 46.6% and 55.8%, respectively.

The parameterization of crop coefficients (kc) is critical for determining a water balance. We used satellite-based and literature-based methods to derive kc values for a distributed hydrologic model. We evaluated the impact of different kc parametrization methods on the water balance and simulated hydrologic response at the basin and sub-basin scale. The hydrological model SPHY was calibrated and validated for a period of 15 years for the upper Segura basin (~2500 km2) in Spain, which is characterized by a wide range of terrain, soil, and ecosystem conditions. The model was then applied, using six kc parameterization methods, to determine their spatial and temporal impacts on actual evapotranspiration, streamflow, and soil moisture. The parameterization methods used include: (i) Normalized Difference Vegetation Index (NDVI) observations from MODIS; (ii) seasonally-averaged NDVI patterns, cell-based and landuse-based; and (iii) literature-based tabular values per land use type. The analysis shows that the influence of different kc parametrization methods on basin-level streamflow is relatively small and constant throughout the year, but it has a bigger effect on seasonal evapotranspiration and soil moisture. In the autumn especially, deviations can go up to about 15% of monthly streamflow. At smaller, sub-basin scale, deviations from the NDVI-based reference run can be more than 30%. Overall, the study shows that modeling of future hydrological changes can be improved by using remote sensing information for the parameterization of crop coefficients.

Assessing the impacts of environmental change on soil erosion and sediment yield at the large catchment scale remains one of the main challenges in soil erosion modelling studies. Here, we present a process-based soil erosion model, based on the integration of the Morgan–Morgan–Finney erosion model in a daily based hydrological model. The model overcomes many of the limitations of previous large-scale soil erosion models, as it includes a more complete representation of crucial processes like surface runoff generation, dynamic vegetation development, and sediment deposition, and runs at the catchment scale with a daily time step. This makes the model especially suited for the evaluation of the impacts of environmental change on soil erosion and sediment yield at regional scales and over decadal periods. The model was successfully applied in a large catchment in southeastern Spain. We demonstrate the model's capacity to perform impact assessments of environmental change scenarios, specifically simulating the scenario impacts of intra- and inter-annual variations in climate, land management, and vegetation development on soil erosion and sediment yield.

Halfway the 20th century, groundwater management in agricultural areas led to channelisation of the majority of lowland streams in the Netherlands. This has led to degradation of the aquatic and terrestrial ecosystems, characteristic for lowland streams. Over the past 25 years, water authorities in the Netherlands have aimed at restoring these degraded streams. Historical maps show that many lowland streams consist of a meandering planform. Re-meandering is the common practice regarding stream restoration in the Netherlands. Little is known about the morphological processes following the completion of such stream restoration projects. The aim of this thesis is to characterize the morphodynamic developments of restored lowland streams, with a focus on meander processes.Three traditional stream restoration projects (Hagmolenbeek, Lunterse beek and Tungelroyse beek) were monitored during the initial two years after construction of the new channel. In these projects, the former straightened channel was replaced by a re-meandered channel. A standardized monitoring plan was implemented, which included three morphological surveys (cross-sections, with a one-year interval), sed- iment sampling (from the initial and final channel bed), habitat pattern surveys (three times per year) and continuous discharge and water level measurements. The morphological measurements revealed that morphodynamic developments are mainly concentrated in the first year following construction. Adjustment of the lon- gitudinal bed profile was the main morphological response. Structures (e.g. bridges and weirs), channel width variation and heterogeneity of the channel substrate caused channel bed incision and aggradation, and hence, channel slope adjustment. Lateral development was observed only in a limited number of channel bends, and was mainly related to floodplain heterogeneity. The habitat surveys showed the occurrence of gravel, silt, vegetation and algae on the channel bed. Morphological developments at the scale of the channel cross-section were exceptional, despite the fine sediment characteristics (median grain size 125-250 μ m). Due to these channel bed characteristics, sediment is transported during the entire year.Water authorities are constantly looking for more cost-effective alternatives for Summary re-meandering. One such method is to remove bank protection and allow autoge- nous processes to develop a sinuous planform. To study these processes, a large- scale field experiment was performed in a 600 m long straight channel reach (Hooge Raam). Over a period of almost three years, the channel was allowed to evolve au- togenously from initially flat-bed conditions, in response to a variable discharge. Alternate bars developed within eight months after the start of the experiment. The initial stages of bar development included bar growth, both in wavelength and in amplitude, and limited bar migration. Towards the end of the experiment, the alternate bar pattern became increasingly irregular and bar amplitudes started to decrease. During the experiment, the channel slope declined from 1.8 m km − 1 to 0.9 m km − 1 . Two bar theories were applied to establish their predictive capacity. Both bar theories predicted the development of alternate bars under the constructed channel conditions and a decreasing likelihood for the development of alternate bars in response to the declining channel slope. This study shows that it is unlikely that the typical sinuous planform in lowland streams, as observed from historical maps, is the result from autogenous processes alone. Exogenous processes, such as a local seepage or floodplain heterogeneity, may be needed to achieve channel sinuosity.Processes of meander initiation were studied focussing on a man-made canal (Gelderns-Nierskanaal). The canal was constructed near the end of the 18th century, as a straight channel between the river Niers (Germany) and the river Meuse (The Netherlands). The banks on the Dutch part of the channel were left unprotected and developed into an active meandering channel, featuring meander development and valley incision. These processes were analysed using historical topographic maps and recent airborne LiDAR data. Meandering initiated in three sections of the chan- nel, where the channel sinuosity developed asynchronously over time. Sedimentary successions in the study area show layers of iron oxide, indicating groundwater seepage from nearby located higher elevated terrains. Only at the spots where meandering had initiated, iron oxide was found close to the surface level. This pro- vides a clue that seepage triggered bank erosion by increasing the moisture content of the banks. The spatial variation in meandering behaviour, as observed in this channel, justifies efforts to implement the influence of floodplain heterogeneity and the effect of seepage on bank erosion in meander models.Backwater effects played a substantial role in the development of a chute cutoff, which occurred after the realization of a stream restoration project in the Lunterse beek. In this stream restoration project, additional measurements were performed, next to the standardized monitoring plan. Over a period of almost 2 years, the additional monitoring included fourteen high-resolution morphological surveys and 156 riparian vegetation mapping. Prior to the cutoff, a plug bar was deposited in the bend to be cutoff. Hydrodynamic model results were used to infer that the plug bar was related to a backwater effect, causing a drop of sediment transport capacity. Upstream from the plug bar, an embayment formed in the floodplain at a location where the former channel was located. The former channel was filled with sediment prior to channel construction, resulting in a less consolidated area of the floodplain. Consequently, it was prone to erosion. The chute channel continued to incise and widen into the floodplain and, after 6 months, acted as the main channel. These results show how upstream sediment supply and backwater effects are involved in the processes that lead to the occurrence of a chute cutoff.The chute cutoff and several additional morphological adjustments occurred in a period without riparian vegetation in the Lunterse beek. Herbaceous vegetation started to develop approximately 7 months after construction, with a maximum coverage by the end of the summer period. Detailed morphological and hydro- logical data show a marked difference in morphological behaviour between the pre-vegetation and post-vegetation stage. A linear regression procedure was ap- plied to relate morphological activity to time-averaged Shields stress. In the initial stage after construction, with negligible riparian vegetation, channel morphology adjusted with a weak response to the discharge hydrograph. In the subsequent period, morphological activity in the showed a clear relation to discharge varia- tion. The two stages of morphological response to the restoration measures may be caused by riparian vegetation development, although additional field measure- ments are needed to substantiate these findings.Lowland streams are small rivers, consisting of a sinuous channel pattern, a sandy channel bed and a gentle slope (<1 m km − 1 ). It is likely that the sinuous planform observed on historical maps is a result from exogenous influences, rather than autogenous processes. In general, the studied lowland streams show little mor- phological activity. The observed morphodynamics occurred mainly in the first year after construction and were caused by backwater effects and floodplain heterogene- ity. After initial morphological adjustments, the channel planform remained stable. The rapid establishment towards an equilibrium state of the channel planform is at odds with the view on lowland streams as small rivers migrating actively in their own deposits. The term re-meandering may be misleading, because of the conno- tation with channel meandering in time. The steadiness of the channel planforms has not been extensively demonstrated over geological time scales. This study has focused on short-term observations, since engineering time scales are more relevant for stream restoration practitioner

We introduce scywalker, an innovative and scalable package developed to comprehensively analyze long-read nanopore sequencing data of full-length single-cell or single-nuclei cDNA. Existing nanopore single-cell data analysis tools showed severe limitations in handling current data sizes. We developed novel scalable methods for cell barcode demultiplexing and single-cell isoform calling and quantification and incorporated these in an easily deployable package. Scywalker streamlines the entire analysis process, from sequenced fragments in FASTQ format to demultiplexed pseudobulk isoform counts, into a single command suitable for execution on either server or cluster. Scywalker includes data quality control, cell type identification, and an interactive report. Assessment of datasets from the human brain, Arabidopsis leaves, and previously benchmarked data from mixed cell lines, demonstrate excellent correlation with short-read analyses at both the cell-barcoding and gene quantification levels. At the isoform level, we show that scywalker facilitates the direct identification of cell-type-specific expression of novel isoforms.Competing Interest StatementWDC and MS have received free consumables and travel reimbursements from Oxford Nanopore Technologies. The other authors report no conflict of interest. Oxford Nanopore Technologies supported this work by providing free PromethION flow cells for sequencing the single-cell plant transcriptomes.