Spatio-temporal scales of hydrological impact assessment in large river basins: the Mekong case

River alterations, being either natural or anthropogenic, have impacted the environment and riverine communities, and nature, throughout human history. During the last two centuries, the scale of the anthropogenic impacts has expanded significantly as a result of larger water resources related projects. Numerous human activities have consequences for the environment measured along multiple scales and levels. The multiscale/-level nature of the problems related to the impact assessment discipline requires that researchers address key issues of scales and levels in their analyses. The thesis aims to present the spatio-temporal scales of the hydrological impact assessment (HIA) process in a large river basin context and analyse how the scales should be taken into account when conducting the assessment. A special focus is on the data and methodologies used within the HIA. The levels of this work are hydrology, hydrodynamics and sediment transport, forming the sub-disciplines of the HIA. The geographical focus is the Mekong River Basin in Southeast Asia where HIA is presented at different scales through seven case studies, based on the appended papers. The Mekong is facing rapid development activities and in this work their consequences on the above-mentioned levels have been analysed and discussed at different scales. Scales are particularly important when a) identifying the critical processes and areas of possible consequences, b) selecting the spatio-temporal scales of the assessment, c) identifying the data needed and available, d) selecting the methodologies and tools related to the process, and e) presenting the results of the assessment to the decision-makers and planners. The thesis concludes that, instead of down-/up-scaling, a multiscale approach often appears to be a more preferable solution. A more extensive inclusion of scale issues in the impact assessment process is believed to contribute to building a more profound connection between researchers and decisions makers

Towards Best Practice Framing of Uncertainty in Scientific Publications: A Review of Water Resources Research Abstracts

Uncertainty is recognized as a key issue in water resources research, amongst other sciences. Discussions of uncertainty typically focus on tools and techniques applied within an analysis, e.g. uncertainty quantification and model validation. But uncertainty is also addressed outside the analysis, in writing scientific publications. The language that authors use conveys their perspective of the role of uncertainty when interpreting a claim —what we call here “framing” the uncertainty. This article promotes awareness of uncertainty framing in four ways. 1) It proposes a typology of eighteen uncertainty frames, addressing five questions about uncertainty. 2) It describes the context in which uncertainty framing occurs. This is an interdisciplinary topic, involving philosophy of science, science studies, linguistics, rhetoric, and argumentation. 3) We analyze the use of uncertainty frames in a sample of 177 abstracts from the Water Resources Research journal in 2015. This helped develop and tentatively verify the typology, and provides a snapshot of current practice. 4) Provocative recommendations promote adjustments for a more influential, dynamic science. Current practice in uncertainty framing might be described as carefully-considered incremental science. In addition to uncertainty quantification and degree of belief (present in ~5% of abstracts), uncertainty is addressed by a combination of limiting scope, deferring to further work (~25%) and indicating evidence is sufficient (~40%) – or uncertainty is completely ignored (~8%). There is a need for public debate within our discipline to decide in what context different uncertainty frames are appropriate. Uncertainty framing cannot remain a hidden practice evaluated only by lone reviewers

Causes and trends of water scarcity in food production

The insufficiency of water resources to meet the needs of food production is a pressing issue that is likely to increase in importance in the future. Improved understanding of historical developments can provide a basis for addressing future challenges. In this study we analyse how hydroclimatic variation, cropland expansion and evolving agricultural practices have influenced the potential for food self-sufficiency within the last century. We consider a food production unit (FPU) to have experienced green–blue water (GBW) scarcity if local renewable green (in soils) and blue water resources (in rivers, lakes, reservoirs, aquifers) were not sufficient for producing a reference food supply of 3000 kcal with 20% animal products for all inhabitants. The number of people living in FPUs affected by GBW scarcity has gone up from 360 million in 1905 (21% of world population at the time) to 2.2 billion (34%) in 2005. During this time, GBW scarcity has spread to large areas and become more frequent in regions where it occurs. Meanwhile, cropland expansion has increased green water availability for agriculture around the world, and advancements in agronomic practices have decreased water requirements of producing food. These efforts have improved food production potential and thus eased GBW scarcity considerably but also made possible the rapid population growth of the last century. The influence of modern agronomic practices is particularly striking: if agronomic practices of the early 1900s were applied today, it would roughly double the population under GBW scarcity worldwide

A conceptual model to guide exploration of global food-water security

While food security can be approached as a local issue, it is strongly influenced by factors at inter-regional and global scales related to production, transaction (e.g. trade and distribution) and consumption, and by drivers such as climate, population growth, diet change, as well as social, political and technological developments. Action on food security therefore benefits from being informed by current global patterns and potential future changes and taking an integrated approach to assessing impacts of proposed responses. Modelling can notably contribute by assessing the influence of various factors on food security. Due to the significant complexity and uncertainty involved, model development and use is simplified by approaching it as an exploratory process rather than aiming for a comprehensive historically accurate model. We present a macro-scale conceptual model to help structure and guide this exploration. We begin with the broad question "Will future developments achieve and maintain food security?" with the intent of exploring alternate possibilities of future developments, definitions of food security and factors influencing this question, beginning with assessing whether there is enough green and blue water to meet dietary energy requirements under typical current and future climatic variation. The conceptual model guides the selection of factors to explore sequentially through modelling (keeping other variables constant), iteratively building complexity as necessary. This helps to construct understanding using manageable building blocks, with the conceptual model evolving as it is used. The staged decomposition of this complex issue provides a framework to help build capacity for individuals and government agencies to understand their actions and policy respectively in a global context, with the hope that improving knowledge of adaptation options can help secure food supply to everyone

Flood severity along the Usumacinta River, Mexico : Identifying the anthropogenic signature of tropical forest conversion

Anthropogenic activities are altering flood frequency-magnitude distributions along many of the world's large rivers. Yet isolating the impact of any single factor amongst the multitudes of competing anthropogenic drivers is a persistent challenge. The Usumacinta River in southeastern Mexico provides an opportunity to study the anthropogenic driver of tropical forest conversion in isolation, as the long meteorological and discharge records capture the river's response to large-scale agricultural expansion without interference from development activities such as dams or channel modifications. We analyse continuous daily time series of precipitation, temperature, and discharge to identify long-term trends, and employ a novel approach to disentangle the signal of deforestation by normalising daily discharges by 90-day mean precipitation volumes from the contributing area in order to account for climatic variability. We also identify an anthropogenic signature of tropical forest conversion at the intra-annual scale, reproduce this signal using a distributed hydrological model (VMOD), and demonstrate that the continued conversion of tropical forest to agricultural land use will further exacerbate large-scale flooding. We find statistically significant increasing trends in annual minimum, mean, and maximum discharges that are not evident in either precipitation or temperature records, with mean monthly discharges increasing between 7% and 75% in the past decades. Model results demonstrate that forest cover loss is responsible for raising the 10-year return peak discharge by 25%, while the total conversion of forest to agricultural use would result in an additional 18% rise. These findings highlight the need for an integrated basin-wide approach to land management that considers the impacts of agricultural expansion on increased flood prevalence, and the economic and social costs involved.Peer reviewe

Cattle Production for Exports in Water-Abundant Areas: The Case of Finland

Water scarcity is a severe global threat, and it will only become more critical with a growing and wealthier population. Annually, considerable volumes of water are transferred virtually through the global food system to secure nations’ food supply and to diversify diets. Our objective is to assess, whether specializing water-intensive production for exports in areas with an abundance of natural resources, would contribute to globally resource-efficient food production. We calculated Finland’s virtual water net export potential (four scenarios) by reallocating the present underutilized agricultural land and combining that with a domestic diet change (three scenarios) to maximize the exports of cattle products. Assessed scenarios indicate that the greatest potential to net export virtual water (3.7 billion m3 year−1, 25-time increase to current) was achieved when local production was maximized with domestic and exported feed, and bovine meat consumption in Finland was replaced with a vegetarian substitute. This corresponds to annual virtual water consumption for food of about 3.6 million global citizens (assuming 1032 m3 cap−1 year−1). Therefore our results suggest, that optimizing water-intensive production to water-rich areas, has a significant impact on global water savings. In addition, increasing exports from such areas by decreasing the domestic demand for water-intensive products to meet the nutrition recommendation levels, saves water resources

The development of the water management system of Angkor: a provisional model

International audienceThe nature and even the existence of water management at Angkor has been the subject of considerable debate since the 1970s. Recent work at Angkor by the EFEO and the Greater Angkor Project has mapped a vast water management network extending across approximately 1000 sq km. From the new map an outline can be provide of the development of the network between the 8 th-9 th and the 14 th centuries. Each large extension of the network tapped water from a succession of natural rivers flowing from NE to SW. Each river was further north and was tapped further to the west. The network had five major components-E-W embankments that trapped water flowing from the north and northeast; N-S channels that eventually delivered water to large reservoirs (baray); the baray and the large temple moats; embankments and channels oriented from NW to SE that could distribute water back from west to east across the slope of the land; and channels oriented towards the southwest which could dispose of water rapidly to the lake, the Tonle Sap. Significantly the later major channels, such as the Angkor Wat canal and the canal that pre-dated the current Siem Reap river, were drains that served to dispose of water into the lake