Optimization of Applied Water Depth Under Water Limiting Conditions

Water productivity is a major challenge in all agricultural regions and despite water shortages, farmers do not welcome water management strategies due to a lack of knowledge of possible economic consequences. This study aimed to introduce the optimum applied water depths under limiting conditions through mathematical optimization. The effects of optimization were coupled with irrigation scheduling to assess yield, water productivity, and net income. Production and cost functions were created based on two scenarios for the applied water. According to the results, the best applied water depth under water limiting conditions depends on land limiting conditions and how severe water limitation is. In mild to moderate water limiting conditions, by using the optimum applied water depth (W_w), water can be saved by 26% causing a 3 to 4% decrease in the net income per unit of land and a 16% increase in the net income per unit of water. As water supply is severely limited, using the equivalent optimum applied water depth (W_ew) results in the highest productivity. Although using W_ew causes a 14 to 17% decrease in the net income per unit of land, it saves water by 46%. In water limiting conditions, if the land is not limited, using W_ew causes the maximum net income per unit of land. A sensitivity analysis was conducted for the net income and the optimum applied water depths, as well. Furthermore, irrigation scheduling caused a 27% increase in the net income per unit of land. Overall, using optimum applied water depths and irrigation scheduling are highly recommended for addressing water scarcity.

     

The Role of Virtual Water Flows in Physical Water Scarcity: The Case of Central Asia

Water scarcity in Central Asia was analyzed by using two water scarcity indices at the scale of sub-basin areas (SBAs): water stress index (consumption-to-availability ratio) and water shortage index (water availability per capita). These indices were calculated for a baseline scenario that included virtual water flows, and again for a scenario where international trade was eliminated, thus assessing the role of virtual water flows in water scarcity. Over 80% of the study area population suffers from water stress and approximately 50% from water shortage as well. Removing virtual water flows considerably decreased water scarcity for approximately half the population. Reducing the exports of water-intensive products could thus be an option, along with other more traditional measures, for alleviating water scarcity in Central Asia.     

Harmonisation of Reliability Performance Indices for Planning and Operational Evaluation of Water Supply Reservoirs

The planning and operational performance evaluation of water supply reservoirs routinely use the volume-based (R_v) and time-based (R_t) reliability indices but decision making is often complicated by trade-off necessitated by the fact that the two are never the same, with R_v ≥ R_t. This study has resolved the problem by harmonising the two indices. Using data from ten global rivers, simulations of hypothetical reservoirs were carried out to determine capacity for specified demands and R_t values. The corresponding R_v values were then evaluated and the resulting reliability biases (i.e. R_v – R_t) were found. To harmonise the two indices, i.e. to nullify the biases, the concept of water shortage threshold was introduced, which is the minimum quantity of water shortage that can be taken as constituting real failure for the purpose of R_t evaluation; shortage quantities below this will be disregarded. The results showed that the water shortage threshold that nullifies the reliability bias can be as high as 60% of the demand, depending on the runoff variability, the demand and the specified R_t. When averaged over all the situations analysed, the water shortage threshold was found to be 51% of the demand. Although this might appear high, it is argued that it is plausible both within the context of developed economies, where unaccounted-for-water can be much higher than 51%, and of underdeveloped economies where large sections of the population have no access to adequate water supply. In the latter case, a reduction of 50% in water supplied that guarantees uninterrupted supply of the other 50% will be deemed satisfactory and reliable, while for the former, a shortage of 50% that forces a change in behaviour to waste less water will also be deemed satisfactory. The significance and novelty of this study stem from the fact that it has removed the need for the trade-off between the two reliability indices, thus enabling unequivocal characterisation of water supply reservoir performance for effective decision making.     

Water Footprint of Grain Product in Irrigated Farmland of China

China faces the dual challenge of grain production pressure and water scarcity. It is significant to reduce water footprint of grain product (WFGP, m³/t) in irrigated farmland. The focus of grain production and agricultural water use, and the precondition is to determine the WFGP and its composition. This paper estimates the WFGP in irrigated farmland of 31 provinces (including municipalities, autonomous regions) a by collecting actual data of 443 typical irrigation districts in 1998, 2005 and 2010, and analyses its temporal and spatial variation in irrigated farmland of China. The result shows that the WFGP in each province decreases with time except in Jiangxi and Hunan, and the average value of all provinces reduced from 1494 m³/t in 1998 to 1243 m³/t in 2010. The WFGP decreases faster in more developed municipal cities and major grain production provinces. The annual average WFGP in irrigated farmland is 1339 m³/t and the blue and green water account for 63.5 % and 36.5 % of the total, respectively. The WFGP and its composition are significantly different between provinces. Generally, provinces distributed inside and beyond Huang-Huai-Hai Plain, have a higher water productivity, lower WFGP and blue water footprint of grain product, while most provinces located in northwest, northeast, southeast and south China have a higher WFGP and lower proportion of green water in the WFGP as a whole. Portion of the blue water footprint (BWFGP) is not consumed for crop evapotranspiration (BWFGP _ET ) but conveyance loss (BWFGP _cl ). The national averaged BWFGP _cl decreases with time and but still remains up to 466 m³/t in 2010, making up 34.8 % of the WFGP. In order to safeguard grain security and ease the water resource pressure, the Chinese government should increase investment and apply advanced technology for developing water-saving agriculture, improve the efficiency of water use and further reduce the WFGP. Considering also the contribution of grain output and the relatively high WFGP, the government should give priority to developing water-saving agriculture in the Northeast of China.     

Water Scarcity Impacts and Potential Conflicts in the MENA Region

Abstract

The failure of water resources to meet the basic requirements of society has a host of social, economic, environmental, and political impacts. This paper addresses those impacts with particular reference to the region of the Middle East and North Africa (MENA). Water scarcity is a manmade phenomenon brought about by the increasing demands of the population for water. The imbalance in the population-water resources equation strains society and has an adverse impact on domestic hygiene, public health, and cost of domestic water, and could impart political problems as serious as bringing down governments. On the social side, water scarcity adversely impacts job opportunities, farm incomes, credibility and reliability of agricultural exports, and the ability of the vulnerable to meet the cost of domestic water. Economically, the adverse impact is displayed in the loss of production of goods, especially agricultural goods, the loss of working hours because of the hardships society faces as a result of water scarcity. The impacts of water scarcity on regional stability are addressed with reference to water in the Middle East Peace Process. Finally, the serious impacts of conflicts and potential water wars are discussed. Water, energy, and environment are triplets. The eventual solution to water scarcity lies in the invention of an energy generating technology that renders the cost of power affordable by societies and that does not impart serious environmental problems.     

Optimal Allocation of Agricultural Water Resources Based on Virtual Water Subdivision in Shiyang River Basin

Without subdividing into blue and green virtual water, the virtual crop water is currently used in the allocation of water resources based on virtual water strategy. In order to improve agricultural water use efficiency and the proportion of green water utilization, a multi-objective optimal allocation model for agricultural water resources is developed in this study. The model is based on the subdivision of virtual water into blue and green virtual water, subject to three objectives of the maximum net benefit from agriculture, the minimum fairness difference in the utilization of water, and the maximum proportion of green water utilization. Taking Shiyang River basin as an example, agricultural water resources are optimized through regional virtual water trade in the basin. Results show that compared with the situation in the year 2007, the net benefit of agriculture, the fairness difference in the utilization of water, and the proportion of green water utilization are optimized. At the same time, the planting ratio of food crops, such as corn, reduces, while the planting ratio of cash crops, such as cotton, vegetables, and fruits, increases. Through regional virtual water strategy in the basin, with the crops of different districts having comparative advantages, the proportion of green water utilization and the blue water use efficiency are improved. The study provides a scientific basis to solve the water shortage problem in the basin.     

Impact of Water Reallocation on the Economy in the Fertile Crescent

Water scarcity is a societal problem in arid and semi-arid regions in the Fertile Crescent (FC). In FC countries, water shortages threaten economic growth, social cohesion, environmental sustainability and political stability. Under drought conditions, water shortages can be mitigated by using water more efficiently and by appropriate allocation of scarce water resources. In this paper water reallocation is addressed by reallocating some agricultural water use for other higher-value uses such as municipal and industrial sectors. Reallocating water from irrigation to other uses can provide sufficient and sustainable water supplies to meet the growing domestic and industrial demands for the next two decades. Most of the literature on water reallocation suggests that shifting water use from agriculture to other sectors would be feasible, but few studies address how much water should be reallocated.. The conceptual model will suppose that there are two users (A and B) and that their economic efficiency can be achieved when MB_A?=?MB_{B, ceteris paribus} . A reallocation of water away from agriculture at 1 % of average total water use per year for the next 20 years for a total reallocation of 20 % by year 20. would increase GDP, could help alleviate the water-scarcity problem in the FC and lead to more efficient use of water. Further work or modeling is less important than is action based on available analyses. All evidence suggests decision-makers would be on solid ground to began re-allocating water in the FC now.     

Man-made Rivers: A New Approach to Water Resources Development in Dry Areas

ABSTRACT

Poor surface and groundwater resources distribution on the national, regional, and global levels has created severe water shortages in several parts of the world. The construction of Man-made Rivers (MMRs) to achieve a more desirable distribution of available water supplies is both technically feasible and economically rational. The Libyan experience with its Great MMR Project is briefly described and its results are introduced as an example to support the above conclusions. Similar future projects may be constructed to serve other water scarcity zones such as the countries of the Middle East, North Africa. and the Southwestern U.S.A.     

Diagnosing Causes of Water Scarcity in Complex Water Resources Systems and Identifying Risk Management Actions

From the water management perspective, water scarcity is an unacceptable risk of facing water shortages to serve water demands in the near future. Water scarcity may be temporary and related to drought conditions or other accidental situation, or may be permanent and due to deeper causes such as excessive demand growth, lack of infrastructure for water storage or transport, or constraints in water management. Diagnosing the causes of water scarcity in complex water resources systems is a precondition to adopt effective drought risk management actions. In this paper we present four indices which have been developed to evaluate water scarcity. We propose a methodology for interpretation of index values that can lead to conclusions about the reliability and vulnerability of systems to water scarcity, as well as to diagnose their possible causes and to propose solutions. The described methodology was applied to the Ebro river basin, identifying existing and expected problems and possible solutions. System diagnostics, based exclusively on the analysis of index values, were compared with the known reality as perceived by system managers, validating the conclusions in all cases.     

Temporal Variability of Water Footprint for Maize Production: The Case of Beijing from 1978 to 2008

The water footprint (WF) of crop production is a comprehensive indicator that can reflect water consumption types, quantities and environmental impacts during the crop growth period. This study assesses interannual variability of green, blue and grey WFs of maize production in Beijing from 1978 to 2008. Results indicate that: (1) The multi-year average WF of maize was 1,031 m³ ton^?1 which was 56 % green, 25 % blue, and 19 % grey; (2) the climate experienced a warm-dry period in Beijing during the period from 1978 to 2008, and this lead to the increase of crop water requirement and irrigation water requirement for maize with trends of 0.52 mm a^?1 and 2.86 mm a^?1, respectively; (3) under the combined effects of climate change and agricultural inputs, the total WF and green WF presented decreasing trends. The blue and grey WFs had clear increasing trends; (4) statistical analysis revealed that interannual variability of green and blue WFs were caused by both climatic factors (effective precipitation) and non-climatic (agricultural inputs) factors. The grey WF was mainly associated with non-climatic factors, such as chemical fertilizers consumption.