Changes In Hydrological Behaviour Research Articles

Partial exclusion of precipitation: throughfall, stemflow and canopy interception in Eucalyptus plantations in southern Brazil

Hydrological behavior in reforested watersheds is different from that under other forms of cover. The variation may be related to aspects intrinsic to species, planting density, physiological maturity, management system and climatic conditions. Periodically, climatic anomalies such as the case of La Ninã are observed, and these are responsible for the alteration of the rainfall regime and consequently generate water deficits in the southern region of Brazil. Water deficit is responsible for reducing growth and productivity for the Eucalyptus genus, in addition to causing changes in hydrological behavior in reforested watersheds. Accordingly, this study compared the partition of rainfall in throughfall, stemflow and canopy interception of eucalyptus trees submitted or not to partial exclusion of precipitation. In the open field, 3 rainfall collectors were installed, and in the stand, for each rain exclusion treatment, 9 throughfall collectors and 9 stemflow collectors were installed. Every two weeks for 12 months, the volume of the collectors was measured. The quantified precipitation was 1627 mm over a year. In the treatment without exclusion, 84.8, 2.9 and 12.3% referred to throughfall, stemflow and canopy interception, respectively, while in the treatment excluding rainfall 80.6, 2.3 and 17.2% referred to throughfall, stemflow and canopy interception. The regression adjustments for throughfall and stemflow showed satisfactory R2 coefficients.

Effects of livestock grazing on soil health and recovery of a degraded Andean Araucaria forest

AbstractAraucaria araucana is an iconic long‐lived endangered tree species native to Southern Chile and Argentina. Araucaria forests and soils provide a myriad of ecosystem benefits to local communities, which are threatened by increasing anthropic‐driven disturbances like fire and livestock overgrazing. The main objectives of this study were: (i) to evaluate the effect of uncontrolled livestock grazing on soil health; and (ii) to identify a set of sensitive soil health indicators to grazing pressure. Twenty soil health indicators in two contiguous degraded forest areas with contrasting grazing pressure were considered. A substantial shift in forest structure and a 12% reduction in tree coverage on the overgrazed sites were observed. Overgrazing has substantially affected soil physical, chemical, and biological health indicators, making soil conditions less suitable for forest regeneration. Significant increments in C:P and N:P ratios were observed due to overgrazing (p < 0.01). Soil chemical properties such as Kjeldahl nitrogen, P‐fractions (total, inorganic, and available), cation exchange capacity (CEC), and pH were identified as the best indicators of overgrazing activity in these soils. Additionally, forest cover reduction and overgrazing altered soil physical indicators (e.g., saturated hydraulic conductivity, infiltration, and aggregate stability), suggesting changes in hydrological behavior with potential consequences in water storage and availability. Our results show that uncontrolled grazing in native protected forests degrades soils and forests, restricting forest regeneration and potentially accelerating erosive processes. These results emphasize the need for improved conservation plans for these endangered forests that systematically evaluates and monitors the direct and indirect effects of livestock grazing on soil health.

Changes in hydrological behaviours triggered by earthquake disturbance in a mountainous watershed

Landslides induced by strong earthquakes often destroy large amounts of landscape vegetation which can trigger significant changes in runoff potential and flood flow. Little is known about hydrological behaviours imposed by co-seismic landslides and their post-earthquake evolution. Therefore, we collected time-series datasets (2007–2018) of underlying surface conditions (USC) changes including landslide expansion and recovery in a watershed affected by the Wenchuan earthquake to further quantify how the large physical disturbance affected the flood hydrological behaviours. The hydrological model HEC-HMS was calibrated and validated to predict the historical hydrological behaviours based on 5 min time-series data in rainfalls and streamflow (2018–2019), showing a good model performance with a mean Nash–Sutcliffe efficiency of 0.76. It was found that, shortly after the earthquake, the sharp expansion with 11% of landslide areas elevated the magnitudes of runoff potential, peak discharge, and runoff volume by >10%, and the peak to time for the high-magnitude flood was advanced by 25 min compared to the pre-earthquake levels. The tipping point along the hydrological disturbance–recovery trajectory was detected within 2011 with higher flood peaks and volumes, and the periods of 2011–2013 (i.e. 3–5 years post-earthquake) were deemed to be a rapid recovery period, revealing an unstable hydrological function. These findings are significant for clearly understanding the magnitude and timing, as well as greater risks of post-earthquake catastrophic flooding in earthquake-stricken regions. Additionally, the post-earthquake accompanied rainstorm-induced geohazards, which limited the recovery of landscape vegetation, triggering an undulant but clear recovery process (1–7 years post-earthquake) of hydrological behaviours. These findings promoted our understanding of the spatiotemporal evolution of hydrological behaviours triggered by the earthquake, and further contribute to the development of adaptation and mitigation strategies for the unpredictable flash floods triggered by future abrupt natural hazards in earthquake-affected regions.

Nonparametric tests for stationary analysis in hydrological data

One of the main problems for water resources management systems has been the climate change and the intensification of anthropogenic activities in river basins. In this context, this work aimed to analyze the dynamics of land use and cover and its influence on temporal variability on streamflow data. The behavior of hydrological data (streamflow and rainfall) over time was analyzed by applying the nonparametric tests of Mann Kendall and Pettitt. Images derived from orbital sensors using the Random Forest classifier assessed the anthropogenic influence in the area, land use, and cover classification. The rainfall data did not present significant changes over time, according to the applied tests. However, the low annual flow and average annual flow presented nonstationary behavior, with a trend of reduction over time. As rainfall did not change in its patterns over time, the main reason associated with the changes in streamflow regimes was associated with the changes in land use and land cover, especially in the areas for crops, that had an increase of 48% in the study period, which can contribute to increase the demand for water and affect the streamflow. The results obtained confirm the importance of this study for water management systems to adapt itself to the changes in hydrological behavior over time.

Runoff and sediment behavior from soil plots contaminated with kerosene and gasoil

Although impacts of several hazardous inputs on the environment have been widely investigated, the role of petroleum contaminations on hydrological behavior of soil has not been sufficiently addressed. Changes in hydrological behavior of contaminated soil generally exert an important influence on the relationship between the infiltration process and runoff generation, causing several environmental threats. This study aimed to investigate the effect of different petroleum levels on runoff generation and sediment yield under simulated natural conditions. Consequently, three levels of Kerosene and Gasoil (0, 130 and 2600 g m−2), and two slopes (5% and 25%) were applied each with three replicates to experimental soil plots. A well-equipped experimental setup was designed and conducted in the rainfall and soil erosion simulation laboratory with a constant 35 mm h−1 rainfall intensity for 30 min. The corresponding flow behavior of plots to governing conditions was continuously monitored and analyzed. Results indicated that both runoff and sediment yield were significantly (p < 0.05) influenced by different types of contaminants. Increasing oil concentrations had maximum impact on the studied variable particularly when the slope was set to5%.Maximumdecrease and increase rates in time to runoff and runoff coefficient were found for 2600 g m−2 Gasoil for a slope of 5%. Comparing the variations in runoff volume and sediment concentration during the rainfall events indicated an obvious difference between these two variables. The runoff volume increased with time, while sediment concentration first reached a peak value and started decreasing afterwards. Gasoil-contaminated soils yielded much larger runoff and sediment compared to that of Kerosene-contaminated soils. The effect of slope on sediment generation was stronger in contaminated soils than in uncontaminated soils. Results further confirmed the significant effect of Gasoil or Kerosene on increasing soil loss due to decreasing infiltration and increasing water repellency. Increase in runoff volume and sediment generation with increasing oil concentration and slope urging the necessity of further considerations to control soil contamination for both soil and water conservation purposes.

Current understanding of hydrological processes on common urban surfaces

Understanding the rainfall-runoff behaviour of urban land surfaces is an important scientific and practical issue as storm water management policies increasingly aim to manage flood risk at local scales within urban areas, whilst controlling the quality and quantity of runoff that reaches receiving water bodies. By reviewing field measurements reported within the literature on runoff, infiltration, evaporation and storage on common urban surfaces, this study describes a complex hydrological behaviour with greater rates of infiltration than often assumed, contradicting a commonly adopted, but simplified classification of the hydrological properties of urban surfaces. This shows that the term impervious surface, or impermeable surface, referring to all constructed surfaces (e.g. roads, roofs, footpaths, etc.) is inaccurate and potentially misleading. The hydrological character of urban surfaces is not stable through time, with both short (seasonal) and long term (decadal) changes in hydrological behaviour, as surfaces respond to variations in seasonal characteristics and degradation in surface condition. At present these changing factors are not widely incorporated into hydrological modelling or urban surface water management planning, with static values describing runoff and assumptions of imperviousness often used. Developing a greater understanding of the linkages between urban surfaces and hydrological behaviour will improve the representation of diverse urban landscapes within hydrological models.

Assessing the impacts of climate change on river flows in England using the UKCP09 climate change projections

Summary This paper presents an assessment of the effects of climate change on river flow regimes in representative English catchments, using the UKCP09 climate projections. These comprise a set of 10,000 coherent climate scenarios, used here (i) to evaluate the distribution of potential changes in hydrological behaviour and (ii) to construct relationships between indicators of climate change and hydrological change. The study uses six catchments, and focuses on change in average flow, high flow (Q5) and low flow (Q95). There is a large range in hydrological change in each catchment between the plausible UKCP09 climate projections, with differences between catchments largely due to differences in catchment geology and baseline water balance. The range in change between the UKCP09 projections is in most catchments smaller than the range between changes with scenarios based on the CMIP3 ensemble of climate models (although the shape of the distribution of changes is different), and earlier UK scenarios produce changes that tend towards the lower (drier) end of the UKCP09 range. The difference between emissions scenarios is small compared to the range across the 10,000 scenarios. Changes in high flows are largely driven by changes in winter precipitation, whilst changes in low flows are determined by changes in summer precipitation and temperature.

Hydrological behaviour of a drained agricultural peat catchment in the tropics. 2: Time series transfer function modelling approach

Transfer function models of the rainfall–runoff relationship with various complexities are developed to investigate the hydrological behaviour of a tropical peat catchment that has undergone continuous drainage for a long time. The study reveals that a linear transfer function model of order one and noise term of ARIMA (1,0,0) best represents the monthly rainfall–runoff relationship of a drained peat catchment. The best-fitted transfer function model is capable of illustrating the cumulative hydrological effects of the catchment when subjected to drainage. Transfer function models of daily rainfall–runoff relationships for each year of the period 1983–1993 are also developed to decipher the changes in hydrological behaviour of the catchment due to drainage. The results show that the amount of rain water temporarily stored in the peat soil decreased and the catchment has become more responsive to rainfall over the study period.Editor Z.W. Kundzewicz; Associate editor D. HughesCitation Katimon, A., Shahid, S., Abd Wahab, A.K., and Shabri, A., 2013. Hydrological behaviour of a drained agricultural peat catchment in the tropics. 2: Time series transfer function modelling approach. Hydrological Sciences Journal, 58 (6), 1310–1325.

The impacts of climate change on river flow regimes at the global scale

Summary This paper presents an assessment of the impacts of climate change on a series of indicators of hydrological regimes across the global domain, using a global hydrological model run with climate scenarios constructed using pattern-scaling from 21 CMIP3 (Coupled Model Intercomparison Project Phase 3) climate models. Changes are compared with natural variability, with a significant change being defined as greater than the standard deviation of the hydrological indicator in the absence of climate change. Under an SRES (Special Report on Emissions Scenarios) A1b emissions scenario, substantial proportions of the land surface (excluding Greenland and Antarctica) would experience significant changes in hydrological behaviour by 2050; under one climate model scenario (Hadley Centre HadCM3), average annual runoff increases significantly over 47% of the land surface and decreases over 36%; only 17% therefore sees no significant change. There is considerable variability between regions, depending largely on projected changes in precipitation. Uncertainty in projected river flow regimes is dominated by variation in the spatial patterns of climate change between climate models (hydrological model uncertainty is not included). There is, however, a strong degree of consistency in the overall magnitude and direction of change. More than two-thirds of climate models project a significant increase in average annual runoff across almost a quarter of the land surface, and a significant decrease over 14%, with considerably higher degrees of consistency in some regions. Most climate models project increases in runoff in Canada and high-latitude eastern Europe and Siberia, and decreases in runoff in central Europe, around the Mediterranean, the Mashriq, central America and Brasil. There is some evidence that project change in runoff at the regional scale is not linear with change in global average temperature change. The effects of uncertainty in the rate of future emissions is relatively small.

Methodology for land use change scenario assessment for runoff impacts: A case study in a north-western European Loess belt region (Pays de Caux, France)

Changes of agricultural land use often induce changes in hydrological behavior of watersheds. Hence, effective information regarding runoff responses to future land use scenarios provides useful support for decision-making in land use planning and management. The objective of this study is to develop a methodology to assess land use change scenario impacts on runoff at the watershed scale. This objective implies translating qualitative information from scenarios into quantitative input parameters for biophysical models. To do so, qualitative information from scenarios should be quantified and spatialized. The approach is based on the combination of 2015 local land use change scenarios (SYSPHAMM method) based on local stakeholders expertise, a model of spatio-temporal allocation of crops to fields (LandSFACTS model) and a watershed runoff model (STREAM model). The study was conducted for regions underlain by silty loamy soils scattered across Northern Europe. It was applied on the Saussay watershed in Upper Normandy (France). The approach is illustrated through runoff assessment of one of the land use change scenarios (characterized by the ending of the set-aside obligation and the disappearance of dairy farming). This scenario appeared relevant for local stakeholders. The methodology presented suggests that assessing local land use scenarios in terms of runoff requires taking into account crop allocation diversity allowed by farmers' decision rules. This requirement accounts for runoff variability at the watershed outlet since crops spatial distribution throughout the watershed, depending on farmers' specific decision rules (i.e. cropping systems), strongly condition runoff phenomenon. Besides, choices regarding scenario implementation (quantification and spatialization) should to be made according to those cropping systems. Accordingly, taking into account crop allocation diversity due to farmers' cropping systems shows that there is a variability in terms of runoff at the watershed outlet (from 19 478 m3 to 35 004 m3 for the winter period and a low-intensity rainfall event for example). This variability can then be explored with local decision makers with the aim of finding solutions reducing runoff risks. The proposed approach provides a useful source of information for assessing the responses of surface runoff of future land use changes. Such scenarios providing impact assessment on runoff should encourage both local policy makers and local actors to actively discuss the future of land use in Upper Normandy.