Water Availability For Agriculture Research Articles

Drought Management Plans and Water Availability in Agriculture. A Risk Assessment Model for a Southern European Basin

The Drought Management Plans (DMPs) are regulatory instruments that establish priorities among the different water uses and define more stringent constraints to access to publicly provided water during droughts, especially for non-priority uses such as agriculture. These plans have recently become widespread across EU southern basins. However, in some of these basins the plans were approved without an assessment of the potential impacts that they may have on the economic activities exposed to water restrictions. This paper develops a stochastic methodology to estimate the expected water availability in agriculture that results from the decision rules of the recently approved DMPs. The methodology is applied to the particular case of the Guadalquivir River Basin in southern Spain. Results show that if DMPs are successfully enforced, available water will satisfy in average 62.2% of current demand, and this figure may drop to 50.2% by the end of the century as a result of climate change. This is much below the minimum threshold of 90% that has been guaranteed to irrigators so far.

Drought management plans and water availability in agriculture: A risk assessment model for a Southern European basin

The Drought Management Plans (DMPs) are regulatory instruments that establish priorities among the different water uses and define more stringent constraints to access to publicly provided water during droughts, especially for non-priority uses such as agriculture. These plans have recently become widespread across EU southern basins. However, in some of these basins the plans were approved without an assessment of the potential impacts that they may have on the economic activities exposed to water restrictions. This paper develops a stochastic methodology to estimate the expected water availability in agriculture that results from the decision rules of the recently approved DMPs. The methodology is applied to the particular case of the Guadalquivir River Basin in southern Spain. Results show that if DMPs are successfully enforced, available water will satisfy in average 62.2% of current demand, and this figure may drop to 50.2% by the end of the century as a result of climate change. This is much below the minimum threshold of 90% that has been guaranteed to irrigators so far.

Leaf water dynamics of Arabidopsis thaliana monitored in-vivo using terahertz time-domain spectroscopy

The declining water availability for agriculture is becoming problematic for many countries. Therefore the study of plants under water restriction is acquiring extraordinary importance. Botanists currently follow the dehydration of plants comparing the fresh and dry weight of excised organs, or measuring their osmotic or water potentials; these are destructive methods inappropriate for in-vivo determination of plants' hydration dynamics. Water is opaque in the terahertz band, while dehydrated biological tissues are partially transparent. We used terahertz spectroscopy to study the water dynamics of Arabidopsis thaliana by comparing the dehydration kinetics of leaves from plants under well-irrigated and water deficit conditions. We also present measurements of the effect of dark-light cycles and abscisic acid on its water dynamics. The measurements we present provide a new perspective on the water dynamics of plants under different external stimuli and confirm that terahertz can be an excellent non-contact probe of in-vivo tissue hydration.

Near‐term acceleration of hydroclimatic change in the western U.S.

Given its large population, vigorous and water‐intensive agricultural industry, and important ecological resources, the western United States presents a valuable case study for examining potential near‐term changes in regional hydroclimate. Using a high‐resolution, hierarchical, five‐member ensemble modeling experiment that includes a global climate model (Community Climate System Model), a regional climate model (RegCM), and a hydrological model (Variable Infiltration Capacity model), we find that increases in greenhouse forcing over the next three decades result in an acceleration of decreases in spring snowpack and a transition to a substantially more liquid‐dominated water resources regime. These hydroclimatic changes are associated with increases in cold‐season days above freezing and decreases in the cold‐season snow‐to‐precipitation ratio. The changes in the temperature and precipitation regime in turn result in shifts toward earlier snowmelt, base flow, and runoff dates throughout the region, as well as reduced annual and warm‐season snowmelt and runoff. The simulated hydrologic response is dominated by changes in temperature, with the ensemble members exhibiting varying trends in cold‐season precipitation over the next three decades but consistent negative trends in cold‐season freeze days, cold‐season snow‐to‐precipitation ratio, and 1 April snow water equivalent. Given the observed impacts of recent trends in snowpack and snowmelt runoff, the projected acceleration of hydroclimatic change in the western U.S. has important implications for the availability of water for agriculture, hydropower, and human consumption, as well as for the risk of wildfire, forest die‐off, and loss of riparian habitat.

Climate change impact on countrywide water balance in Bolivia

There is increasing concern about the ongoing reduction in water supplies in the tropical Andes due to climate change effects such as glacier/snow melting resulting from rising air temperatures. In addition, extreme events and population growth are already directly affecting life and water renewability in the country. A countrywide integrated national plan for improving basin-scale water management in Bolivia is needed to assure water availability for agriculture, industry, mining, and human consumption. This study aims to provide a modeling tool to assess Bolivia’s past, current, and future water availability and identify basins at risk of water deficits. The Soil Water Assessment Tool was used to simulate the monthly water balance from 1997 to 2008, as well as the water balance projected to 2050 for the entire country. It considers possible changes in air temperatures and precipitation proposed by 17 Global Circulation Models as well as carbon dioxide projections derived from the Special Report Emission Scenario. Overall, model results were close to satisfactory compared to observations, with some exceptions due to lack of information for expanding the timeline and improving calibration. Based on the calculation of three hydrologic indicators, the study identifies basins that would be the most susceptible to water deficits for a baseline from 1997 to 2008, and in the event of the projected climate change, to 2050.

Is shrinking groundwater resources leading to socioeconomic and environmental degradation in Central Ganga Plain, India?

In India, agriculture is a source of livelihood for over 64 % of the country's population. Indo-Gangetic Plains of North India support good cultivation and provides livelihood to several hundred million people. The climatic change studies have documented changes in precipitation pattern which can alter the flow pattern discharge to the reservoirs and availability of water for agriculture. The reduction in groundwater recharge through reduced rainfall and irregularity in surface water availability has increased dependence on groundwater resources causing its overexploitation. Consequently, pumping from deeper groundwater conditions need more energy and pump efficiency for abstraction which ultimately requires huge capital investment. Moreover, volatile fuel prices make the agricultural society vulnerable to economic losses. The repercussions of water level decline are likely to disseminate an additional economic burden to the groundwater user community. To cope with higher energy demands, increase in fuel consumption has led to environmental degradation through higher carbon emission. Thus, the groundwater depletion is likely to have far-reaching socioeconomic and environmental impacts which are not confined to the Central Gangetic Plain. In the present study, attempts have been made to analyze the effect of groundwater depletion as a commodity in the social framework of the region.

Effect of Phosphorus and Irrigation Levels on Yield, Water Productivity, Phosphorus Use Efficiency and Income of Lowland Rice in Northwest Pakistan

With decreasing availability of water for agriculture and increasing demand for rice production, an optimum use of irrigation water and phosphorus may guarantee sustainable rice production. Field experiments were conducted in 2003 and 2004 to investigate the effect of phosphorus and irrigation levels on yield, water productivity (WP), phosphorus use efficiency (PUE) and income of low land rice. The experiment was laid out in randomized complete block design with split plot arrangements replicated four times. Main plot consisted of five phosphorus levels, viz. 0 (P0), 50 (P50), 100 (P100), 150 (P150), and 200 (P200) kg/hm2, while subplots contained of irrigation times, i.e. 8 (I8), 10 (I10), 12 (I12), and 14 (I14) irrigation levels, each with a water depth of 7.5 cm. Mean values revealed that P150 in combination with I10 produced the highest paddy yield (9.8 t/hm2) and net benefit (1 231.8 US$/hm2) among all the treatments. Phosphorus enhanced WP when applied in appropriate combination with irrigation level. The highest mean WP [13.3 kg/(hm2·mm)] could be achieved at P150 with I8 and decreased with increase in irrigation level, while the highest mean PUE (20.1 kg/kg) could be achieved at P100 with I10 and diminished with higher P levels. The overall results indicate that P150 along with I10 was the best combination for sustainable rice cultivation in silty clay soil.

On the attribution of changing pan evaporation in a nature reserve in SW China

AbstractNegative trends of measured pan evaporation are widely reported. Studies of the factors that underlie this reduction in pan evaporation have not reached a consensus about the controlling factors. Most studies employ statistical analysis (correlation analysis or stepwise regression) to identify the controlling climatic variables; in contrast, few studies have employed physical‐based theories. In addition, observations of pan evaporation and related climatic variables are reported to be influenced by anthropogenic activities. Consequently, the observed trends of climatic variables in a nature reserve would be useful for understanding regional climate change. The present study site is located in Ailaoshan National Nature Reserve, SW China, which is free of anthropogenic activity. In this study, we firstly applied the adjusted PenPan model to estimate the pan evaporation. Then, using this physical‐based model, we identified a positive trend in pan evaporation, with a much larger increase in the dry season than in the wet season. The model results indicate that the change in the aerodynamic component is larger than that in the radiative component. In contrast to the reduction in wind speed and sunshine hours that has been reported in previous studies at various sites, we found that wind speed and sunshine hours have increased in recent decades, thereby explaining the increase of the pan evaporation rate. Wind speed made the greatest contribution to the change in pan evaporation, followed by sunshine duration. This study indicates that the potential evaporation has increased at this site despite the widely reported reduction in measured pan evaporation. During the dry season, the availability of water for agriculture and agroforestry could be threatened. Copyright © 2012 John Wiley & Sons, Ltd.

Impact of Climate and Land-Use Changes on Water Security for Agriculture in Northern China

North China is the most important food basket of China, where the majority of wheat and corn are produced. Most crops grown in North China are irrigated, thus water security is food security. Since the 1980s, drying has been frequently observed, as shown by a reduction in precipitation, cutoff in riverflow, and shrinkage of lakes. This increase in drying cannot be explained by climate change alone. We propose that intensive land-use in this area in recent decades has had a significant impact. The objectives of the study are to develop a quantitative model of the concurrent processes of climate change and land-use in North China, and to estimate the relative contributions of each on the observed drying. We integrated relevant socioeconomic data, land-use data, and climate data in the model, and carried out a detailed multitemporal (decade, year, day) analysis. Results showed that land-use has greatly changed since 1999. This change is mainly associated with an extremely important 1999 national policy of “returning farmland and grazing land to forest and grassland”. We found an interesting interaction between climate change and land use policy on riverflow, runoff, and evapotranspiration. During 1970s and 1980s, climate change explained more than 80%, while the land-use change explained only 10% of the riverflow change. The relative contributions were 45 and 45% in the 1980s-1990s and 35 and 55% in the 1990s-2000s respectively for climate change and land-use change. Since the 1990s land-use change has also contributed more to runoff change than climate change. The opposite trend was found for changes in evapotranspiration. Water availability for agriculture in northern China is simultaneously stressed by extensive changes in land-use and rapid climate change. Adaptation of ecological principles, such as the “returning farmland/grazing land to forest and grassland” policy, and other adjustments of economic developmental strategies can be effective tools to mitigate the water shortage problem in northern China and promote sustainable agricultural and food development.

Infrastructure and Growth

Physical Infrastructure stocks in Pakistan since the last two decades have been growing at a very low pace which resulted in increasing unemployment and very low economic growth in the last four years. The paper analyses the link between infrastructure, productivity and growth in Pakistan by applying two distinct methodologies—growth accounting and growth regressions. We find out that infrastructure stock has significantly positive impact on productivity and economic growth. At the individual level, electricity generation, agricultural water availability and telecommunications impact the economic growth positively and significantly, while, roads development have no impact. This is an indication of over investment in roads, especially highways. Based on model findings, we recommended that Pakistan will have to increase the allocation of PSDP to above 1.5 percent of the GDP if the problem of shortage of electricity is to be addressed on a priority basis so as to raise the growth rate of the economy.

Layering Precision Land Leveling and Furrow Irrigated Raised Bed Planting: Productivity and Input Use Efficiency of Irrigated Bread Wheat in Indo-Gangetic Plains

Stagnating yield and declining input use efficiency in irrigated wheat of the Indo-Gangetic Plain (IGP) coupled with diminishing availability of water for agriculture is a major concern of food security in South Asia. The objective of our study was to establish an understanding of how wheat yield and input use efficiency can be improved and how land leveling and crop establishment practices can be modified to be more efficient in water use through layering of precision-conservation crop management techniques. The “precision land leveling with raised bed” planting can be used to improve crop yield, water and nutrient use efficiency over the existing “traditional land leveling with flat” planting practices. We conducted a field experiment during 2002-2004 at Modipuram, India to quantify the benefits of alternate land leveling (precision land leveling) and crop establishment (furrow irrigated raised bed planting) techniques alone or in combination (layering precision-conservation) in terms of crop yield, water savings, and nutrient use efficiency of wheat production in IGP. The wheat yield was about 16.6% higher with nearly 50% less irrigation water with layering precision land leveling and raised bed planting compared to traditional practices (traditional land leveling with flat planting). The agronomic (AE) and uptake efficiency (UE) of N, P and K were significantly improved under precision land leveling with raised bed planting technique compared to other practices.

Yellow River basin: living with scarcity

The Yellow River basin is a key food production centre of global importance facing rapidly growing water scarcity. Water availability for agriculture in the basin is threatened by rapid growth in the demand for industrial and urban water, the need to flush sediment from the river's lower reaches, environmental demands and growing water pollution. Climate change is already evident in the basin with long-term declines in river runoff, higher temperatures, and increasing frequency and intensity of drought. The Chinese government has exhausted most options for improving water supply. The challenge will be to switch to improved water demand management, which is hampered by existing governance structures, and lack of integrated agriculture and water resource policies.

Can farmers extend their cultivation areas in urban agriculture? A contribution from agronomic analysis of market gardening systems around Mahajanga (Madagascar)

The rapid urbanization in developing countries implies an increasing pressure on urban agriculture for production. As most perishable food products come from this agriculture in close proximity to population concentrations, we analysed from an agronomic point of view how market-garden farmers can meet this increasing urban demand. This work took place in the case of Mahajanga, a secondary city with high increasing demographic rate on the Northwest coast of Madagascar. Based on preliminary surveys to characterize the farming systems (on a sample of 91 farms), 11 market-garden farmers chosen in the three main agricultural zones of the urban area were surveyed during two years. Surveys aimed at understanding their decision rules in crop choices, crop allocation to land and resource management, and to estimate their room for manoeuvre to increase their leafy vegetable areas under cultivation. The wholesalers and retailers who buy the farmers’ produce were also surveyed. A previous model of decision rules regarding crop location on farm territory was used to analyse the on-farm surveys and cartographic methods (GIS and on-farm manual representations) were used to quantify the land use. We highlight the following major points. (1) The leafy vegetable production in the surveyed farms already intensively uses land: farmers have complex decision rules largely depending on the water dynamics in the two main environments (lowlands and lakesides) where leafy vegetables are cultivated during the dry season. (2) The scarcity of farmers’ resources (labour money and water) leads to very little internal room for manoeuvre to increase the leafy vegetable production in the farms. (3) At territorial level however, some land reserve exist in one of the lowlands, but not on lakesides. The water availability for agriculture must be better informed through specialized hydrologic studies, as one of the main constraints nowadays to extend the agricultural area. An extrapolation to other cases of urban agriculture is then discussed as well as the role of agronomy to help urban planners to consider the place of agriculture in the urban development.

Competition for water for the food system

Although the global agricultural system will need to provide more food for a growing and wealthier population in decades to come, increasing demands for water and potential impacts of climate change pose threats to food systems. We review the primary threats to agricultural water availability, and model the potential effects of increases in municipal and industrial (M&I) water demands, environmental flow requirements (EFRs) and changing water supplies given climate change. Our models show that, together, these factors cause an 18 per cent reduction in the availability of worldwide water for agriculture by 2050. Meeting EFRs, which can necessitate more than 50 per cent of the mean annual run-off in a basin depending on its hydrograph, presents the single biggest threat to agricultural water availability. Next are increases in M&I demands, which are projected to increase upwards of 200 per cent by 2050 in developing countries with rapidly increasing populations and incomes. Climate change will affect the spatial and temporal distribution of run-off, and thus affect availability from the supply side. The combined effect of these factors can be dramatic in particular hotspots, which include northern Africa, India, China, parts of Europe, the western US and eastern Australia, among others.

Decision Support Systems to Manage Water Resources for Irrigation at District Level in Southern Italy Using Remote Sensing Information. An Integrated Project

In this number of the Italian Journal of Agronomy, ten scientific papers are published on the results obtained from the AQUATER project (along with one keynote), which were presented during a final conference held in Bari, Italy on 12-13 May 2009. The rationale of this project, supported by Ministry of Agriculture, Food and Forestry policies in the framework of Research and Development for areas of Southern Italy, is based on the consideration that the availability of irrigation water for agriculture is becoming ever more limited due to climate change, a deterioration in water quality and an increase in irrigated areas. Consequently, agricultural research must provide guidelines and products in order to achieve the sustainable use of such an important natural resource.

Climate change, water availability and future cereal production in China

Climate scenarios from a regional climate model are used to drive crop and water simulation models underpinned by the IPCC A2 and B2 socio-economic development pathways to explore water availability for agriculture in China in the 2020s and 2040s. Various measures of water availability are examined at river basin and provincial scale in relation to agricultural and non-agricultural water demand and current and planned expansions to the area under irrigation. The objectives are to understand the influences of different drivers on future water availability to support China's food production. Hydrological simulations produce moderate to large increases in total water availability in response to increases in future precipitation. Total water demand increases nationally and in most basins, but with a decreasing share for agriculture due primarily to competition from industrial, domestic and municipal sectors. Crop simulations exhibit moderate to large increases in irrigation water demand which is found to be highly sensitive to the characteristics of daily precipitation in the climate scenarios. The impacts of climate change on water availability for agriculture are small compared to the role of socio-economic development. The study identifies significant spatial differences in impacts at the river basin and provincial level. In broad terms water availability for agriculture declines in southern China and remains stable in northern China. The combined impacts of climate change and socio-economic development produce decreases in future irrigation areas, especially the area of irrigated paddy rice. Overall, the results suggest that there will be insufficient water for agriculture in China in the coming decades, due primarily to increases in water demand for non-agricultural uses, which will have significant implications for adaptation strategies and policies for agricultural production and water management.

Performance of a New Capacitance Soil Moisture Probe in a Sandy Soil

Rapid population growth and increasing urban demand reduce the availability of water for agriculture in Florida. The water‐holding capacity of sandy soils in the Central Florida Ridge area is very poor (<0.10 m3 m−3). Improved soil water monitoring probes can help growers manage irrigation more efficiently and conserve water. This study evaluated a new soil water probe (ECH2O EC‐5 sensor, Decagon Devices, Pullman, WA) in terms of probe‐to‐probe signal variability, response to fertilizer‐induced salinity, and changes in soil temperature, soil volume sampled, sensitivity to pockets of air or dry soil, and performance in the field. Results were compared with an earlier version of a Decagon probe, the EC‐20. Results indicated that the new probe has several advantages. The EC‐5 was not sensitive to salinity or temperature fluctuations. Probe output change was almost zero when the salinity of the soil was increased by adding fertilizer to a soluble solids concentration of 14 g kg−1 When temperature was changed gradually from 3 to ∼38°C, probe output increased by only about 1%. Soil volume sampled by the probe was about 15 cm3 The change in probe response was negligible when soil cores up to 0.95 cm in diameter near the probe surface were removed. Probes responded well to changes in soil water content in the field. The EC‐5 probe output increased noticeably when bulk density was increased from 1.1 to 1.6 Mg m−3 Probe‐to‐probe output signal and response to bulk density variations can affect the estimation of field water content unless necessary correction factors are utilized. These probes can be useful for monitoring soil water movement, estimating soil water content, and scheduling irrigation.

Introduction. Sustainable agriculture

Today, global agriculture feeds a population of approximately 6.4 billion and delivers a wide range of additional services. These range from waste management and water purification through delivery of fuel, fibre and chemical products to recreation and the conservation of biodiversity. Significant

Precipitation analysis and agricultural water availability in the Southern Highlands of Yemen

AbstractRain‐fed agriculture with supplementary irrigation, usually referred to as ‘water harvesting on terraced fields’ is the traditional irrigation technique in the Ta'izz area, located in the southern uplands of the Yemen Mountain Massif. The non‐traditional method of groundwater irrigation has recently led to overuse and depletion of aquifers. A new orientation towards the traditional agricultural irrigation techniques is necessary for the purpose of sustainability. This requires a better scientific understanding of these irrigation systems. In order to understand the design and management of water harvesting schemes, rainfall analysis and the identification of prevailing rainfall patterns is required. A statistical rainfall analysis was conducted to detect the probability of rainfall exceedance during the vegetation period from May until October. Rainfall supply was then measured against water requirements of the prevailing crop Sorghum bicolore. To explore the beneficial effect of the local runoff irrigation schemes, also referred to as water harvesting schemes, water‐harvesting factors were introduced. The rainfall is supplemented by a water‐harvesting factor to show the amplifying effect of those water‐harvesting measures.Analysis results show that a lack of rainfall during the end of the first rainy season and an intermediate dry period under pure rain‐fed conditions can be mitigated by the local runoff irrigation schemes. A fairly reliable and sufficient rainfall characterizes the second rainy season. Copyright © 2005 John Wiley & Sons, Ltd.

Management of Irrigation for Vegetables: Past, Present, and Future

Vegetables are grown throughout the U.S. on various soil types and in various climates. Irrigation is essential to supplement rainfall in all areas to minimize plant water stress. In the U.S., irrigated vegetable production accounts for about 1.9 million ha or 7.5% of the irrigated area. California, Florida, Idaho, Washington, Texas, Nebraska, Oregon, Wisconsin, and Arizona account for 80% of the U.S. production of irrigated vegetables. In the U.S., surface and subsurface (seepage) irrigation systems were used initially and are currently used on 45% of all irrigated crops with a water use efficiency of 33%. Sprinkler or overhead irrigation systems were developed in the 1940s and are currently used extensively throughout the vegetable industry. Sprinkler systems are used on 50% of the irrigated crop land and have a water use efficiency of 75%. In the late 1960s, microirrigation (drip or trickle) systems were developed and have slowly replaced many of the sprinkler and some of the seepage systems. Microirrigation is currently used on 5% of irrigated crops. This highly efficient water system (90% to 95%) is widely used on high value vegetables, particularly polyethylene-mulched tomato (Lycopersicon esculentum), pepper (Capsicum annuum), eggplant (Solanum melongena), strawberry (Fragaria ×ananassa), and cucurbits. Some advantages of drip irrigation over sprinkler include reduced water use, ability to apply fertilizer with the irrigation, precise water distribution, reduced foliar diseases, and the ability to electronically schedule irrigation on large areas with relatively smaller pumps. Drip systems also can be used as subsurface drip systems placed at a depth of 60 to 90 cm. These systems are managed to control the water table, similar to that accomplished with subsurface irrigation systems, but with much greater water use efficiency. Future irrigation concerns include continued availability of water for agriculture, management of nutrients to minimize leaching, and continued development of cultural practices that maximize crop production and water use efficiency.