Environmental impact assessment of water-saving irrigation systems across 60 irrigation construction projects in northern China

With increasing water shortages partly due to increasing demands, water has become a globally relevant issue especially in arid and semi-arid regions. Water-saving irrigation technologies provide new ways for improving the efficiency of water use for agricultural production. Although efficient irrigation management could lead to water savings and increased yields, the water consumption and greenhouse gas emissions during the construction of irrigation projects also puts pressure on environmental health. However, little research has considered the environmental impact of the construction process and materials. To fill this gap, the water footprint (WF) and carbon footprint (CF) of irrigation projects were calculated using life cycle assessment (LCA) methods. The results for sixty typical irrigation projects in northern China showed that the WF accounted for only 0.2–1.5% of the total agricultural WF and 2.3–8.8% of the water saved. When the WF to construct modern irrigation systems is not considered, the water-saving effects of these systems are generally overestimated by 13%. The CF for irrigation projects was 42.0% of all agricultural activities. Due to the difficulty to obtain detailed information for irrigation projects, this paper established the relationship between financial investment or area and CF for three kinds of irrigation projects. It provided a simple quantitative method for assessing its environmental impacts. By comparing environmental impacts and production benefits under different scenarios, using drip irrigation over the long-term could increase crop yield and reduce water footprint, but carbon footprint was increased at the same time. This study suggests that it is necessary to assess the environmental impacts of irrigation construction projects from a life cycle perspective rather focusing only on yield increases and reductions in irrigation amounts.</p

Water and carbon risks within hydropower development on national scale

The United Nations has proposed Sustainable Development Goals (SDGs), which aim to achieve coordinated green development in energy, economic and environmental dimensions. Hydropower is currently the world's most important renewable energy source, it has made up for the electricity shortage and created great economic value, but at the same time, the environmental impacts occurred cannot be ignored. However, current studies focused on a single or a few specific projects, it has not achieved quantitative environmental assessment on regional scale. To fill this gap, we selected China, the world's largest developing country, as the case for the first time to assess the hydropower water footprint (WF) and carbon footprint (CF) at both spatial and temporal dimensions. The results showed that total WF & CF of hydropower in China are 13.90 billion m3 (closes to half annually runoff of the Yellow River) and 413.39 billion kg eqCO2 (is equivalent to burning 1.5 billion t of coal), with intensity of 53.95 m3/MWh and 125.89 kg eqCO2/MWh respectively. The hydropower WF alone is more than regional available water occurred in 1/4 provinces of China. The emission reduction effect of hydropower is overestimated by 11.72 %, this should be considered in plans that hydropower replacing thermal power. Considering the CF of hydropower itself, 25–53 % of the regional carbon emission reduction target would not be achieved. From a global perspective, there about 1/3 countries’ hydropower WF exceed 10 % of the water resource availability, and about 1/4 countries’ hydropower CF exceeds 5 % of carbon emission

Streamflow droughts aggravated by human activities despite management

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems

Streamflow droughts aggravated by human activities despite management

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems

Streamflow droughts aggravated by human activities despite management

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems