This study investigated whether the representative elementary area (REA) concept can be adopted in catchments with multiple geologies. We observed stream discharge at 65 points and water chemistry at 157 points in a 55 km2 catchment that included multiple geologies. At observation points with uniform geology, stream chemistry became constant beyond about 1 km2 in granodiorite and volcanic rocks. At observation points with multiple geologies, spatial variability remained large beyond a few square kilometers. SiO2 and Mg2+ concentrations became constant above 10 km2, but Ca2+ and electrical conductivity did not become constant until 55 km2. Our calculations revealed that for areas of 1–17 km2, almost all of the observed variables were explained by mixing based on geological percentages. However, at greater than 17 km2, the observed values were higher than the calculated values. Therefore, in regions with multiple geologies, the range of the REA with single-parameter geology was confirmed. In our catchments, the REA concept was applicable to areas of 1–17 km2, but areas larger than 17 km2 was outside the range.
We used Landsat satellite images to determine the areal change between 1988 and 2010 of the Condoriri glacier in Bolivia and found that the area decreased by 41% during that period. Moreover, the interannual pattern of recession and expansion of the glacier coincided with warm and cold phases of El Niño/La Niña-Southern Oscillation (ENSO), respectively. Because the glacier recedes more during El Niño events than it expands during La Niña events, the net result is a retreating trend, which, if it continues, means that the glacier will disappear completely by 2035. ENSO frequency increased during the latter part of the 20th century, and ENSO events may become more frequent with continued climate change. Therefore, it is urgent to take measures to adapt Bolivian water management to the loss of glacier meltwater.
This work analyzes hydroclimate projections in Panama toward the end of the 21st century by employing the MRI-AGCM3.1 model. Understanding the impact of climate change on water resources is fundamental for a number of economic activities in Panama (i.e. Panama Canal operation, hydropower generation, and agriculture). Therefore, it is important to assess hydroclimatic impacts in specific basins using reliable Atmospheric Global Circulation Models (AGCMs) validated against actual field data. A 20-km mesh experiment was developed by using time-sliced analysis for current (1979–2002) and future (2075–2099) periods. Uncertainty in climate projections were addressed by completing 60-km mesh AGCM ensemble experiments at three additional lower boundary conditions. Four regions in Panama were selected for detailed analysis: from east to west, Bocas del Toro, Veraguas, Panama Canal and Darien. Projections show significant precipitation increases from May and July to December for all regions except Bocas del Toro. In this region, a decrease in precipitation is expected between April and August. Total runoff for all regions followed the changes in precipitation as expected. Due to net radiation increases, projected evaporation did not appear to be affected by precipitation changes.
This study tried to make a first evaluation of SMOS L2 soil moisture data (ver. 4.00) obtained during ascending orbits using in situ hydrological observation data of a 120 km by 120 km study area on the Mongolian Plateau from April to August in 2010 and from May to September in 2011. Unfortunately, as we could hardly obtain any available data of SMOS L2 soil moisture from descending orbits for evaluation because of Radio Frequency Interferences (RFI), the evaluation results of SMOS L2 soil moisture products only from ascending orbits (5:30–7:00 in local time) were actually analyzed. Although SMOS slightly underestimated the soil moisture contents at a depth of 3 cm, good matching was observed in the response patterns of SMOS and in situ soil moisture data and the differences between these factors were not large. Accordingly, small values of RMSE and bias were obtained between SMOS soil moisture and in situ measured soil moisture at a depth of 3 cm. SMOS was able to estimate surface soil moisture contents with an accuracy of about 0.045 (m3 m−3) in steppe areas of the Mongolian Plateau.
We projected future river discharge in the Chao Phraya River basin and evaluated the uncertainty in future climate projections by using different resolutions and ensemble experiments of the Atmospheric General Circulation Model of the Meteorological Research Institute (MRI-AGCM). We also obtained estimates of precipitation, evaporation, runoff, and river discharge under climate conditions projected for the late 21st century. The results show that precipitation is projected to significantly increase in the future during April to August, excluding May. The projected river discharge at Nakhon Sawan located in the central region shows a peak in September, a delay of one month after the maximum monthly mean precipitation. The estimated reduction in river discharge for January and February was robust based on all members of the 60-km mesh MRI-AGCM ensembles changing in the same direction as that of the 20-km mesh MRI-AGCM. The uncertainty assessment conducted in this study could lead to increased robustness in projected changes in mean river discharge in the late 21st century for this basin.