INTERCOMPARISON OF HYDROLOGICAL MODELING PERFORMANCE WITH MULTI-OBJECTIVE OPTIMIZATION ALGORITHM IN DIFFERENT CLIMATES

Performances of hydrological models vary from basin to basin in different climate conditions. The problem of further identifying how performances vary with climate conditions remains a research challenge for the discipline of hydrology. With the objective of studying this problem, several hydrological models such as HYMOD, NAM and TOPMODEL were applied to 11 basins located in Asian countries with different climate conditions. The multi-objective optimization method Non-dominated Sorting Genetic Algorithm (NSGAII) was used for model calibration and obtaining optimal parameter sets for ensemble modeling. A tendency between the model performances and the aridity index (the ratio of annual potential evaporation to precipitation) was found, which might help us improve understanding of the model performances in different climates and select appropriate models for catchments in different climates

Development and Interpretation of New Sediment Rating Curve Considering the Effect of Vegetation Cover for Asian Basins

Suspended sediment concentration of a river can provide very important perspective on erosion or soil loss of one river basin ecosystem. The changes of land use and land cover, such as deforestation or afforestation, affect sediment yield process of a catchment through changing the hydrological cycle of the area. A sediment rating curve can describe the average relation between discharge and suspended sediment concentration for a certain location. However, the sediment load of a river is likely to be undersimulated from water discharge using least squares regression of log-transformed variables and the sediment rating curve does not consider temporal changes of vegetation cover. The Normalized Difference Vegetation Index (NDVI) can well be used to analyze the status of the vegetation cover well. Thus long time monthly NDVI data was used to detect vegetation change in the past 19 years in this study. Then monthly suspended sediment concentration and discharge from 1988 to 2006 in Laichau station were used to develop one new sediment rating curve and were validated in other Asian basins. The new sediment model can describe the relationship among sediment yield, streamflow, and vegetation cover, which can be the basis for soil conservation and sustainable ecosystem management

Remote sensing based analysis of recent variations in water resources and vegetation of a semi-arid region

This study is designed to demonstrate use of free remote sensing data to analyze response of water resources and grassland vegetation to a climate change induced prolonged drought in a sparsely gauged semi-arid region. Water resource changes over Hulun Lake region derived from monthly Gravity Recovery and Climate Experiment (GRACE) and Tropical Rainfall Measuring Mission (TRMM) products were analyzed. The Empirical Orthogonal Functions (EOF) analysis results from both GRACE and TRMM showed decreasing trends in water storage changes and precipitation over 2002 to 2007 and increasing trends after 2007 to 2012. Water storage and precipitation changes on the spatial and temporal scale showed a very consistent pattern. Further analysis proved that water storage changes were mainly caused by precipitation and temperature changes in this region. It is found that a large proportion of grassland vegetation recovered to its normal state after above average rainfall in the following years (2008-2012) and only a small proportion of grassland vegetation (16.5% of the study area) is degraded and failed to recover. These degraded grassland vegetation areas are categorized as ecologically vulnerable to climate change and protective strategies should be designed to prevent its further degradation

Analysis of River Basin Management in Madagascar and Lessons Learned from Japan

River basins in Madagascar are prone to water scarcity and conflicts of use, which are projected to worsen due to climate change. Therefore, effective integrated water resources management (IWRM) is key. This review examines the current condition of IWRM in Madagascar, evaluates its sustainability, and compares it with the one in Japan. The effects of climate change were analyzed using Aqueduct data. Madagascar has established an IWRM legal framework aligned with the Sustainable Development Goals; however, its application remains limited. For Japan, it was useful to establish IWRM for floods, water utilization, and environmental conservation. This study analyzes the future projections of water availability and demand for the 12 major river basins of Madagascar. Climate change will reduce water availability; the West and the East will experience water stress; the demand will be higher in the highlands, with less water available in the south. The proposed framework and Japan’s experience in river basin management can contribute to solving those problems. The findings of this study serve to enhance the knowledge on IWRM and the impact of climate change in Madagascar; they also suggest actions to be taken by the Malagasy government

Analysis of River Basin Management in Madagascar and Lessons Learned from Japan

River basins in Madagascar are prone to water scarcity and conflicts of use, which are projected to worsen due to climate change. Therefore, effective integrated water resources management (IWRM) is key. This review examines the current condition of IWRM in Madagascar, evaluates its sustainability, and compares it with the one in Japan. The effects of climate change were analyzed using Aqueduct data. Madagascar has established an IWRM legal framework aligned with the Sustainable Development Goals; however, its application remains limited. For Japan, it was useful to establish IWRM for floods, water utilization, and environmental conservation. This study analyzes the future projections of water availability and demand for the 12 major river basins of Madagascar. Climate change will reduce water availability; the West and the East will experience water stress; the demand will be higher in the highlands, with less water available in the south. The proposed framework and Japan’s experience in river basin management can contribute to solving those problems. The findings of this study serve to enhance the knowledge on IWRM and the impact of climate change in Madagascar; they also suggest actions to be taken by the Malagasy government

Attribution analyses of impacts of environmental changes on streamflow and sediment load in a Mountainous basin, Vietnam

Located in the southeastern China and northern Vietnam, the Red River is an important international trans-boundary river that has experienced rapid deforestation and environmental changes over the past decades. We conducted attribution analysis of impacts of various environmental changes on streamflow and sediment load. The contribution of reclassified environmental changes to total change of the streamflow and sediment load was separated. Land cover change based on climate-induced and human-induced indicators were defined. We found that human-induced land cover change was the main factor affecting changes of the streamflow and sediment load. Changes of the land cover were more pronounced in the dry season than in the wet season whereas sediment load changed more in the wet season than in the dry season. In addition, changes in sediment load were mainly caused by human-induced land cover change and the changes of land cover were more influential on sediment load than on streamflow in the Red River basin

Rural drinking water issues in India’s drought-prone area: a case of Maharashtra state

Obtaining sufficient drinking water with acceptable quality under circumstances of lack, such as droughts, is a challenge in drought-prone areas of India. This study examined rural drinking water availability issues during a recent drought (2012) through 22 focus group discussions (FGDs) in a drought-prone catchment of India. Also, a small chemical water quality study was undertaken to evaluate the suitability of water for drinking purpose based on Bureau of Indian Standards (BIS). The drought that began in 2011 and further deteriorated water supplies in 2012 caused a rapid decline in reservoir storages and groundwater levels that led, in turn, to the failure of the public water supply systems in the Upper Bhima Catchment. Dried up and low-yield dug wells and borewells, tanker water deliveries from remote sources, untimely water deliveries, and degraded water quality were the major problems identified in the FGDs. In addition to severe drinking water scarcity during drought, the quality of the drinking water was found to be a major problem, and it apparently was neglected by local governments and users. Severe contamination of the drinking water with nitrate-nitrogen, ammonium-nitrogen, and chlorides was found in the analyzed drinking water samples. Hence, in addition to the water scarcity, the results of this study point to an immediate need to investigate the problem of contaminated drinking water sources while designing relief measures for drought-prone areas of India

Evaluation of the use of global satellite–gauge and satellite-only precipitation products in stream flow simulations

Abstract Satellite remote-sensing products with high spatial and time resolution are expected to provide alternative data sources for data-sparse regions. This study clarifies if the satellite–gauge product outperforms the satellite-only product by comparing remote-sensing precipitation products: one that incorporates rain gauge data (GSMaP-Gauge) and one that uses satellite only (GSMaP-MVK). The appropriateness of those two commonly used high-resolution products as the input to the conceptual hydrological model Hydrologiska Byråns Vattenbalansavdelning for stream flow prediction was also investigated. In addition, we also analyzed the deviations of model parameters due to the bias in remote-sensing precipitation inputs compared to standard ground measurements. The results indicated that GSMaP-Gauge was superior, with satisfactory to good performances in predicting stream flow in both temperate and subtropical basins (Hyeonsan, Fuji, and Da). However, its performance was slightly worse than GSMaP-MVK in the Upper-Cau basin, which was explained by the poor quality of the adjusted data source due to sparse data and the satellite–gauge blending algorithm of GSMaP-Gauge. Better parameter agreements with the observations of GSMaP-Gauge than GSMaP-MVK were found in the Hyeonsan and Da river basins where GSMaP-Gauge showed almost consistent relationship of monthly rainfall compared to ground measurements

Assessment of the Latest GPM-Era High-Resolution Satellite Precipitation Products by Comparison with Observation Gauge Data over the Chinese Mainland

The Global Precipitation Mission (GPM) Core Observatory that was launched on 27 February 2014 ushered in a new era for estimating precipitation from satellites. Based on their high spatial–temporal resolution and near global coverage, satellite-based precipitation products have been applied in many research fields. The goal of this study was to quantitatively compare two of the latest GPM-era satellite precipitation products (GPM IMERG and GSMap-Gauge Ver. 6) with a network of 840 precipitation gauges over the Chinese mainland. Direct comparisons of satellite-based precipitation products with rain gauge observations over a 20 month period from April 2014 to November 2015 at 0.1° and daily/monthly resolutions showed the following results: Both of the products were capable of capturing the overall spatial pattern of the 20 month mean daily precipitation, which was characterized by a decreasing trend from the southeast to the northwest. GPM IMERG overestimated precipitation by approximately 0.09 mm/day while GSMap-Gauge Ver. 6 underestimated precipitation by −0.04 mm/day. The two satellite-based precipitation products performed better over wet southern regions than over dry northern regions. They also showed better performance in summer than in winter. In terms of mean error, root mean square error, correlation coefficient, and probability of detection, GSMap-Gauge was better able to estimate precipitation and had more stable quality results than GPM IMERG on both daily and monthly scales. GPM IMERG was more sensitive to conditions of no rain or light rainfall and demonstrated good capability of capturing the behavior of extreme precipitation events. Overall, the results revealed some limitations of these two latest satellite-based precipitation products when used over the Chinese mainland, helping to characterize some of the error features in these datasets for potential users