Influence of Headwater Reservoirs on Climate Change Impacts and Flood Frequency in the Kabul River Basin

While climate change impacts vary globally, for the Kabul River Basin (KRB), concerns are primarily associated with frequent flooding. This research describes the influence of headwater reservoirs on projections of climate change impacts and flood frequency, and how the riparian countries can benefit from storing of floodwaters for use during dry seasons. Six climate change scenarios and two Representative Concentration Pathways (RCPs) are used in three periods of a quarter-century each. The Soil and Water Assessment Tool (SWAT) is used to assess how the proposed reservoirs will reduce flooding by ~38% during the wet season, reduce the flood frequency from five to 25 years return period, and increase low flows by ~110% during the dry season, which reflect an ~17.5% reduction in the glacier-covered area by the end of the century. The risks and benefits of reservoirs are highlighted in light of the developmental goals of Afghanistan and Pakistan.

Cambios ambientales en los últimos 1800 años en el manglar de Neguanje, Parque Nacional Natural Tayrona, Caribe colombiano

We reconstructed changes in vegetation and climate conditions during the last 1800 years in a column of sediment 4 m deep (Playa Pozo sector, Neguanje Bay, Tayrona National Natural Park, department of Magdalena, Colombia). We characterized the main components (mineral elements, organic matter), micro-stratigraphy (types of organic matter), humidity variations (%), organic and inorganic carbon, and palynological associations (specifically pollen grains), and counted spores of fungi, algae, ferns, plant debris, and insects. The palynological associations (dominant elements) were defined and related to the current types of vegetation. The definition of the dominant groups in the palynological spectrum and their relationship with the current vegetation types was associated with the stratigraphic conditions of the sediments to detect the changes that occurred during this period. In the reconstruction of the paleoenvironments, we determined the relationship between the defined palynological associations and the stratigraphy of the sediments, the humidity (precipitation), and the covered area. For this purpose, we used the temperature calibration curves of the last 2000 years proposed by various authors. We did not recover enough palynomorphs at the base of the column between 400 and 380 cm deep (2000-1693 years BP), but organic components of marine origin predominated in the sediment, a condition associated with a warm period in the central and eastern Colombian Caribbean coastal environments. In zone I (1693-1294 years B.P.), the mangrove was consolidated and in zone II (1294-1078 years A.P.), it expanded with the vegetation of flooded areas. In zone III (1078-654 years B.P.), we detected the occurrence of the greatest mangrove development, especially by the dominant species Rhizophora mangle. In zones IV and V (654 years A.P.-present), the mangrove cover decreased. This period was less warm than the previous ones, similar to the prevailing conditions in the Ciénaga Grande de Santa Marta and its surroundings.

Influence of Supraglacial Debris Thickness on Thermal Resistance of the Glaciers of Chandra Basin, Western Himalaya

A large number of glaciers in the Hindu-Kush Himalaya are covered with debris in the lower part of the ablation zone, which is continuously expanding due to enhanced glacier mass loss. The supraglacial debris transported over the melting glacier surface acts as an insulating barrier between the ice and atmospheric conditions and has a strong influence on the spatial distribution of surface ice melt. We conducted in-situ field measurements of point-wise ablation rate, supraglacial debris thickness, and debris temperature to examine the thermal resistivity of the debris pack and its influence on ablation over three glaciers (Bara Shigri, Batal, and Kunzam) in Chandra Basin of Western Himalaya during 2016–2017. Satellite-based supraglacial debris cover assessment shows an overall debris covered area of 15% for Chandra basin. The field data revealed that the debris thickness varied between 0.5 and 326 cm, following a spatially distributed pattern in the Chandra basin. The studied glaciers have up to 90% debris cover within the ablation area, and together represent ∼33.5% of the total debris-covered area in the basin. The supraglacial debris surface temperature and near-surface air temperature shows a significant correlation (r = > 0.88, p = < 0.05), which reflects the effective control of energy balance over the debris surface. The thermal resistivity measurements revealed low resistance (0.009 ± 0.01 m2°C W−1) under thin debris pack and high resistance (0.55 ± 0.09 m2°C W−1) under thick debris. Our study revealed that the increased thickness of supraglacial debris significantly retards the glacier ablation due to its high thermal resistivity.

A Comparison of National Water Model Retrospective Analysis Snow Outputs at SNOTEL Sites Across the Western U.S.

This study compares the U.S. National Water Model (NWM) reanalysis snow outputs to observed snow water equivalent (SWE) and snow-covered area fraction (SCAF) at SNOTEL sites across the Western U.S. SWE was obtained from SNOTEL sites, while SCAF was obtained from MODIS observations at a nominal 500 m grid scale. Retrospective NWM results were at a 1000 m grid scale. We compared results for SNOTEL sites to gridded NWM and MODIS outputs for the grid cells encompassing each SNOTEL site. Differences between modeled and observed SWE were attributed to both model errors, as well as errors in inputs, notably precipitation and temperature. The NWM generally under-predicted SWE, partly due to precipitation input differences. There was also a slight general bias for model input temperature to be cooler than observed, counter to the direction expected to lead to under-modeling of SWE. There was also under-modeling of SWE for a subset of sites where precipitation inputs were good. Furthermore, the NWM generally tends to melt snow early. There was considerable variability between modeled and observed SCAF as well as the binary comparison of snow cover presence that hampered useful interpretation of SCAF comparisons. This is in part due to the shortcomings associated with both model SCAF parameterization and MODIS observations, particularly in vegetated regions. However, when SCAF was aggregated across all sites and years, modeled SCAF tended to be more than observed using MODIS. These differences are regional with generally better SWE and SCAF results in the Central Basin and Range and differences tending to become larger the further away regions are from this region. These findings identify areas where predictions from the NWM involving snow may be better or worse, and suggest opportunities for research directed towards model improvements.

Modelling Snowmelt Runoff from Tropical Andean Glaciers under Climate Change Scenarios in the Santa River Sub-Basin (Peru)

Effects of climate change have led to a reduction in precipitation and an increase in temperature across several areas of the world. This has resulted in a sharp decline of glaciers and an increase in surface runoff in watersheds due to snowmelt. This situation requires a better understanding to improve the management of water resources in settled areas downstream of glaciers. In this study, the snowmelt runoff model (SRM) was applied in combination with snow-covered area information (SCA), precipitation, and temperature climatic data to model snowmelt runoff in the Santa River sub-basin (Peru). The procedure consisted of calibrating and validating the SRM model for 2005–2009 using the SRTM digital elevation model (DEM), observed temperature, precipitation and SAC data. Then, the SRM was applied to project future runoff in the sub-basin under the climate change scenarios RCP 4.5 and RCP 8.5. SRM patterns show consistent results; runoff decreases in the summer months and increases the rest of the year. The runoff projection under climate change scenarios shows a substantial increase from January to May, reporting the highest increases in March and April, and the lowest records from June to August. The SRM demonstrated consistent projections for the simulation of historical flows in tropical Andean glaciers.

Influence of the Height in a Colombian Multi-Tunnel Greenhouse on Natural Ventilation and Thermal Behavior: Modeling Approach

The dimensions of a passive greenhouse are one of the decisions made by producers or builders based on characteristics of the available land and the economic cost of building the structure per unit of covered area. In few cases, the design criteria are reviewed and the dimensions are established based on the type of crop and local climate conditions. One of the dimensions that is generally exposed to greater manipulation is the height above the gutter and the general height of the structure, since a greenhouse with a lower height has a lower economic cost. This has led some countries in the tropical region to build greenhouses that, due to their architectural characteristics, have inadequate microclimatic conditions for agricultural production. The objective of this study was to analyze the effect on air flows and thermal distribution generated by the increase of the height over gutter of a Colombian multi-tunnel greenhouse using a successfully two-dimensional computational fluid dynamics (CFD) model. The simulated numerical results showed that increasing the height of the greenhouse allows obtaining temperature reductions from 0.1 to 11.7 °C depending on the ventilation configuration used and the external wind speed. Likewise, it was identified that the combined side and roof ventilation configuration (RS) allows obtaining higher renovation indexes (RI) in values between 144 and 449% with respect to the side ventilation (S) and roof ventilation (R) configurations. Finally, the numerical results were successfully fitted within the surface regression models responses.

Composting of fine fraction after mechanical-biological treatment of municipal solid waste

One of most common types of municipal solid waste treatment is mechanical-biological treatment (MBT), which in practice has many variations depending on the method of conducting the technological process and it is possible to get different output fractions. In this paper is analysed waste generated after the MBT with biodrying, where waste after mechanical treatment undergoes process of biodrying, and then is RDF (recovery derived fuel) separated. Fine fraction remains with a high content of organic matter that without additional processing cannot be disposed of on a landfill. The aim of this research was to determine the possibility of fine fraction composting in different conditions – in the open, in the open and covered area, and indoors. In each area are formed three compost piles: 100% fine fraction (KH1, KH4, and KH7), 70% fine fraction and 30% wood chips (KH2, KH5, and KH8), 50% fine fraction and 50% wood chips (KH3, KH6, and KH9). Moisture content, temperature and dissolved organic carbon (DOC) were monitored. Results show that after 13 weeks samples KH1, KH4, and KH7 (100% content of fine fractions) did not achieve DOC value less than 3 000 mg/l. The most effective composting in terms of reducing the DOC is achieved in samples KH3, KH6, KH9. Based on results obtained, it can be concluded that by adding wood chips in fine fraction in ratio 50:50, the most effective and fastest reduction of organic matter is achieved in the analysed samples.