The color of water: The contributions of green and blue water to agricultural productivity in the Western Brazilian Amazon

Abstract. Human activities and climate factors both affect the availability of water resources and the sustainability of water management. Especially in already dry regions, water has become more and more scarce with increasing requirements from growing population, economic development and diet shifts. Although progress has been made in understanding variability of runoff, the impacts of climate variability and human activities on flows of both green water (actual evapotranspiration) and blue water (discharge accumulated in the river network) remain less well understood. We study the spatial patterns of blue and green water flows and the impacts on them of human activities and climate variability as simulated by the Soil and Water Assessment Tool (SWAT) for an inland Heihe river basin located in Northwest China. The results show that total green and blue water flow increased from 1980 to 2005, mainly as a result of climate variability (upward precipitation trends). Direct human activities did not significantly change the total green and blue water flow. However, land use change led to a transformation of 206 million m3 from green to blue water flow, while farmland irrigation expansion resulted in a transformation of 66 million m3 from blue to green water flow. The synchronous climate variability caused an increase of green water flow by 469 million m3 and an increase of blue water flow by 146 million m3 at the river basin level, while the geographical distribution showed an uneven change even with reductions of water flows in western sub-basins at midstream. The results are helpful to benchmark the water resources in the context of global change in the inland river basins in China. This study also provides a general approach to investigate the impacts of historical human activities and climate variability on green and blue water flows at the river basin level.

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Simulation of Green and Blue Water Impacts Caused by Climate Changes in the Apucaraninha River Watershed, Southern Brazil (Simulação dos Impactos da Água Verde e Azul Causados pelas Mudanças Climáticas na Bacia Hidrográfica do Rio Apucaraninha...)

Revista Brasileira de Geografia Física ◽

10.26848/rbgf.v8.1.p179-186 ◽

2015 ◽

Vol 8 (1) ◽

pp. 179

Author(s):

Isabela Raquel Ramos Iensen ◽

Gilson Bauer Schultz ◽

Irani Dos Santos

Keyword(s):

Climate Change ◽

Climate Changes ◽

Green Water ◽

Future Climate Change ◽

Blue Water ◽

Climate Scenarios ◽

Southern Brazil ◽

River Watershed ◽

Hydrological Conditions ◽

Green And Blue Water

Climate changes may generate significant impacts in the hydrological cycle. It is important to recognize modifications in green water (water stored in soil followed by the consumption of the vegetation) and blue water (water that flows into rivers, lakes, wetlands and shallow aquifers) availability in consequence of climate change modifications. The mathematical modelling is used to simulate the effect of climate change scenarios in hydrological processes in watersheds. This study aimed to evaluate the impacts of climate change in blue and green water in Apucaraninha River Watershed, Southern Brazil, considering the climate scenarios A2 and B2, pessimistic and optimistic, respectively, about greenhouse gases emissions developed by IPCC. SWAT was calibrated and validated using daily streamflow from 1987 to 2012. Climate scenarios A2 and B2 were used to simulate the hydrological conditions for the period 2071-2100. The model presented satisfactory fit compared to the observed data allowing the simulation of the current hydrological conditions, therefore permitting the simulation of future climate change impacts on green and blue water. We found that despite the increase in potential evapotranspiration of 19% and 12% for A2 and B2 scenario respectively, caused by the increase in temperature, the reduction in rainfall amount induced to a reduction in actual evapotranspiration, which correspond to green water, and a reduction of 1% for A2 scenario and 14% for B2 scenario in blue water availability.

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Assessment of spatial and temporal patterns of green and blue water flows under natural conditions in inland river basins in Northwest China

Hydrology and Earth System Sciences ◽

10.5194/hess-16-2859-2012 ◽

2012 ◽

Vol 16 (8) ◽

pp. 2859-2870 ◽

Cited By ~ 90

Author(s):

C. F. Zang ◽

J. Liu ◽

M. van der Velde ◽

F. Kraxner

Keyword(s):

River Basin ◽

River Basins ◽

Heihe River Basin ◽

Green Water ◽

Heihe River ◽

Blue Water ◽

Natural Conditions ◽

Water Flows ◽

Inland River ◽

Green And Blue Water

Abstract. In arid and semi-arid regions freshwater resources have become scarcer with increasing demands from socio-economic development and population growth. Until recently, water research and management has mainly focused on blue water but ignored green water. Furthermore, in data poor regions hydrological flows under natural conditions are poorly characterised but are a prerequisite to inform future water resources management. Here we report on spatial and temporal patterns of both blue and green water flows that can be expected under natural conditions as simulated by the Soil and Water Assessment Tool (SWAT) for the Heihe river basin, the second largest inland river basin in Northwest China. Calibration and validation at two hydrological stations show good performance of the SWAT model in modelling hydrological processes. The total green and blue water flows were 22.05–25.51 billion m3 in the 2000s for the Heihe river basin. Blue water flows are larger in upstream sub-basins than in downstream sub-basins mainly due to high precipitation and a large amount of snow and melting water in upstream. Green water flows are distributed more homogeneously among different sub-basins. The green water coefficient was 87%–89% in the 2000s for the entire river basin, varying from around 80%–90% in up- and mid-stream sub-basins to above 90% in downstream sub-basins. This is much higher than reported green water coefficients in many other river basins. The spatial patterns of green water coefficients were closely linked to dominant land covers (e.g. snow cover upstream and desert downstream) and climate conditions (e.g. high precipitation upstream and low precipitation downstream). There are no clear consistent historical trends of change in green and blue water flows and the green water coefficient at both the river basin and sub-basin levels. This study provides insights into green and blue water endowments under natural conditions for the entire Heihe river basin at the sub-basin level. The results are helpful to benchmark the natural flows of water in the basin as part of improved water resources management in the inland river basins of China.

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Green and blue water dimensions of foreign direct investment in biofuel and foodproduction in West Africa

Handbook of Land and Water Grabs in Africa ◽

10.4324/9780203110942-24 ◽

2012 ◽

pp. 337-358

Author(s):

Fred Kizito ◽

Timothy O. Williams ◽

Matthew McCartney ◽

Teklu Erkossa

Keyword(s):

Foreign Direct Investment ◽

West Africa ◽

Direct Investment ◽

Blue Water ◽

Green And Blue Water

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Assessment of Water Footprint for Koshi River Basin (KRB), Nepal

10.5194/egusphere-egu2020-4395 ◽

2020 ◽

Author(s):

Raj Deva Singh ◽

Kumar Ghimire ◽

Ashish Pandey

Keyword(s):

River Basin ◽

Water Use ◽

Crop Production ◽

Agricultural Land ◽

Water Footprint ◽

Green Water ◽

Blue Water ◽

Total Water ◽

Green And Blue Water ◽

Koshi River Basin

Nepal is an agrarian country and almost one-third of Gross Domestic Product (GDP) is dependent on agricultural sector. Koshi river basin is the largest basin in the country and serves large share on agricultural production. Like another country, Nepalese agriculture holds largest water use in agriculture. In this context, it is necessary to reduce water use pressure. In this study, water footprint of different crop (rice, maize, wheat, millet, sugarcane, potato and barley) have been estimated for the year 2005 -2014 to get the average water footprint of crop production during study period. CROPWAT model, developed by Food and Agriculture Organization (FAO 2010b).For the computation of the green and blue water footprints, estimated values of ET (the output of CROPWAT model) and yield (derived from statistical data) are utilised. Blue and green water footprint are computed for different districts (16 districts within KRB) / for KRB in different years (10 years from 2005 to 2014) and crops (considered 7 local crops). The water footprint of crops production for any district or basin represents the average of WF production of seven crops in the respective district or basin.The study provides a picture of green and blue water use in crop production in the field and reduction in the water footprint of crop production by selecting suitable crops at different places in the field. The Crop, that has lower water footprint, can be intensified at that location and the crops, having higher water footprint, can be discontinued for production or measure for water saving technique needs to be implemented reducing evapotranspiration. The water footprint of agriculture crop production can be reduced by increasing the yield of the crops. Some measures like use of an improved variety of seed, fertilizer, mechanized farming and soil moisture conservation technology may also be used to increase the crop yields.The crop harvested areas include both rainfed as well as irrigated land. Agricultural land occupies 22% of the study area, out of which 94% areas are rainfed whereas remaining 6% areas are under irrigation. The study shows 98% of total water use in crop production is due to green water use (received from rainfall) and remaining 2 % is due to blue water use received from irrigation (surface and ground water as source). Potato has 22% blue water proportion and contributes 85% share to the total blue water use in the basin. Maize and rice together hold 77% share of total water use in crops production. The average annual water footprint of crop production in KRB is 1248 cubic meter/ton having the variation of 9% during the period of 2005-2014. Sunsari, Dhankuta districts have lower water footprint of crop production. The coefficient of variation of water footprint of millet crop production is lower as compared to those of other crops considered for study whereas sugarcane has a higher variation of water footprint for its production.

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