Water withdrawals for human use can reduce water in lakes and streams, with significant consequences for aquatic biota. Urbanization, particularly large lawn areas associated with low-density residential development, increases demand on freshwater resources. Outdoor water use accounts for the largest proportion of residential water use during the summer months, which corresponds to the lowest water levels in freshwater ecosystems. Prior studies have sought to understand property features associated with the highest water use; however, these studies do not consider other types of water use nor do they capture the decisions by residents that result in outdoor water use. Understanding these decisions is critical for developing policies and education tools that reduce outdoor water use by changing people’s water use behavior. Focusing on the Ipswich River Watershed, which has been impacted by extreme low flows due to water withdrawals, a mixed-methods approach was used to understand residents’ outdoor water use and the factors influencing the amount and timing of water use. To quantify water use meters were placed on outdoor spigots at residences, participants were provided with a written survey before and after water metering, and in-person interviews were conducted. Irrigation systems used the most water; however, garden watering occurred as frequently as lawn irrigation and many participants indicated that their garden was a primary factor in water use decisions. Participants’ water use decisions fell into categories from habitual (i.e., watering at the same time of day) to purely cognitive (i.e., watering based on weather and plant needs). While many participants felt that water conservation was necessary, their willingness to implement landscape-level conservation practices, such as rain barrels, did not differ from participants who believed water conservation was unnecessary. Interestingly, many residents reduced their outdoor water use behavior and increased their concern for other environmental issues in response to study participation. To have the greatest impact on overall water use, efforts should focus on residents running irrigation systems on a schedule. Outreach should emphasize individualized approaches to water conservation, regardless of water source (public or private), and include information and conservation options specific to the water needs of the individual property.

Limited research has been conducted and uncertainty exists regarding sugarcane response to water stress during different development phases. This information is necessary to optimize the allocation of limited irrigation water for sugarcane production. The objective of this study was to understand and quantify the response of crop water use (CWU), canopy development, stalk elongation, biomass accumulation and partitioning, and sugarcane yield to mild water stress, imposed through deficit drip irrigation, during different development phases. A field experiment consisting of a plant and first ratoon crop of cultivar N49 was conducted near Komatipoort. For the three water stress treatments, available soil water (ASW) was maintained between 30 and 60% of capacity during the tillering phase (TP), stalk elongation phase (SEP) and through both phases. ASW was maintained above 60% of capacity in the well-watered control and during periods when stress was not intended. Rainfall prevented water stress from developing in the TP of the plant crop. In the ratoon crop, 72% less irrigation was applied in the TP, resulting in 50 days of stress (ASW<50%). This did not affect stalk population but reduced CWU by 13%, shortened stalks by 21% and affected the canopy by reducing green leaf number (GLN) and green leaf area index (GLAI). Relieving the stress during SEP allowed the crop to re-establish its canopy, capture adequate photosynthetically active radiation (PAR) and restore rates of photo-assimilation (as suggested by CWU) and stalk elongation to support rapid biomass production. This restoration of plant processes allowed the ratoon crop to attain a cane and stalk dry biomass (SDM) yield that was only 9 and 11% lower (statistically insignificant), respectively, than the well-watered control at lodging (crop age of 286 days). During the SEP of the plant and ratoon crop, 42 and 85% less irrigation was applied, resulting in the crops experiencing 74 and 39 days of stress and using 7 and 8% less water, respectively. This did not affect stalk population or the crop canopy, but reduced stalk height by about 6 and 14% in the plant and ratoon crops, respectively. In both crops, shorter stalks and a negatively affected CWU which reduced photo-assimilate production, reduced cane yield by 14 and 10% (statically insignificant) and SDM yield by 15 and 5% (statistically insignificant), in the plant and ratoon crops respectively. © University of Pretoria iv Deficit irrigation throughout the TP and SEP of the ratoon crop reduced irrigation amount by 74%, resulting in 110 days of stress and reducing CWU by 16% and stalk height by 14%. PAR capture was reduced through reduced GLAI. This resulted in a significant reduction of 15% in cane yield. SDM yield was reduced by 17%, although this was not statistically significant. Stalk sucrose content was not influenced by deficit irrigation but was rather dependent on the duration of the drying-off period prior to harvest. Sucrose yields were therefore largely determined by SDM. Results suggest that the soil water potential (SWP) measured at 0.25 and 0.40 m depths, halfway between drip emitters within a plant or ratoon crop, can drop to about -40 kPa before irrigation is applied, without sacrificing cane or sucrose yield. Lastly, a ratoon crop can rapidly recover from stress during the TP, provided that the SWP during SEP is maintained above -40 kPa. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Plant Production and Soil Science / unrestricted

Irrigation with saline waters is an agricultural practicethat is becoming increasingly common as competition for freshwater increases. In this thesis the mechanisms behind salinityand drought stress has been studied using data from fieldexperiments in combination with a modelling tool, theCoupModel. Measurements from field experiments on salinity,boron toxicity and drought stressed tomatoes grown during twoclimatically different seasons in the Arava desert, Israel,showed a linear relationship between relative growth andevapotranspiration, for all treatments and seasons. Data fromthe spring was used to concurrently simulate growth andtranspiration, hence accounting for feedback mechanisms betweenthe plant and the environment. Salinity stress was modelled asan osmotic effect (reduction of water uptake at high soilsalinities, W approach) or a toxicity effect (direct reductionof photosynthesis with soil salinity, G approach). Goodagreement between simulated growth and transpiration wasachieved with both salinity stress approaches, with twoexceptions. When growth and transpiration were simulated withthe W approach at different salinity levels, transpiration wasunderestimated at high stress. The G approach resulted in anunderestimation of growth at high water stress under moderatesalinity. A direct decrease of photosynthesis leads to adecreasing water-use efficiency with salinity while water-useefficiency remains constant with salinity when the salinitystress is modelled as a reduction in water uptake. Measurementsshowed decreasing water-use efficiency for the salinitygradient, explaining why the W approach was not applicable. Itwas not possible to detect any considerable differences betweenthree different approaches for water uptake tested in thestudy. <b>Keywords:</b>Water-use efficiency; osmotic effect; iontoxicity; semi-arid. / NR 20140805

>Magister Scientiae - MSc / The climate variability and climate change-induced events experienced worldwide have caused a significant decrease in the rainfall volume. South Africa is considered to be one of the driest countries in the world, as it receives an average annual rainfall that is lower than the global annual average. To sustain and grow the agricultural sector, South Africa supplements the low rainfall with its freshwater resources, for irrigation purposes. This action is necessary, especially for meeting the high water requirements of the South African fruit industry, as it is one of the major exporters of fruit in the world. Research has been conducted in an attempt to accurately quantify the water requirements of various fruits, which will assist farmers to save water, to increase their productivity and to managing their irrigation water. However, a knowledge of the water use, actual water consumption rates and the factors that drive them, is minimal and inadequate, and this has had a detrimental effect on the effective management of irrigation water and water allocation by the responsible stakeholders.

Access to high quality, reliable freshwater resources has been recognized as a global issue for decades and as the demand for water continues to grow, water management and sustainability issues have been pushed into the limelight. Despite this mounting pressure, variation in water use practices continues to persist, which contributes to both local and global water security challenges. Drawing on the environmental management literature, I noticed that the majority of the existing research focuses on the role of managerial demographics rather than on the process of how managers think, interpret, and act in strategic situations. Thus, in an effort to address this gap I adopted a qualitative research approach, conducting semi-structured interviews with managers at craft breweries in Alberta and California. My findings indicate that managerial sensemaking acts as a mediating process in a manager’s choice of water management strategy, ultimately influencing their brewery’s water use performance. And, that these relationships are affected by managerial characteristics as well as contextual factors. As the world’s demand for fresh water, and the number of people living in water stressed conditions continues to rise, these findings have important implications. By both extending and contributing to existing sensemaking and cognitive frame theory, my findings shed light on alternative cognitive determinants driving water use variation and thus support the development of more sustainable water management practices.

Species in the genus Populus (poplars) have shown the potential to be utilized as short rotation woody crops for bioenergy production in the Southeast. A lack of knowledge on which poplar taxa perform best on marginal sites throughout the Southeast exists. Through measurement of relationships between growth metrics, water usage and physiological parameters of 2400 poplar trees, I was able to assess: 1) early rotation suitability of numerous poplar varietals to be grown as bioenergy feedstocks in northeast Mississippi, and 2) the effectiveness of early rotation physiological parameters in predicting future productivity and water usage. Overall findings from this study suggest that trees with D x M parentage may be best fit for large-scale plantation growth in the Southeast. They demonstrated low mortality and collectively grew the tallest of all taxa. Early-rotation physiology demonstrated mixed results in predicting future growth and water usage. Findings from this study will be used in future bioenergy feedstock selection.

No description available.

Yes / The Planetary Boundaries (PB) framework represents a significant advance in specifying the ecological constraints on human development. However, to enable decision-makers in business and public policy to respect these constraints in strategic planning, the PB framework needs to be developed to generate practical tools. With this objective in mind, we analyse the recent literature and highlight three major scientific and technical challenges in operationalizing the PB approach in decision-making: first, identification of thresholds or boundaries with associated metrics for different geographical scales; second, the need to frame approaches to allocate fair shares in the 'safe operating space' bounded by the PBs across the value chain and; third, the need for international bodies to co-ordinate the implementation of the measures needed to respect the Planetary Boundaries. For the first two of these challenges, we consider how they might be addressed for four PBs: climate change, freshwater use, biosphere integrity and chemical pollution and other novel entities. Four key opportunities are identified: (1) development of a common system of metrics that can be applied consistently at and across different scales; (2) setting 'distance from boundary' measures that can be applied at different scales; (3) development of global, preferably open-source, databases and models; and (4) advancing understanding of the interactions between the different PBs. Addressing the scientific and technical challenges in operationalizing the planetary boundaries needs be complemented with progress in addressing the equity and ethical issues in allocating the safe operating space between companies and sectors.

No

Crop coefficients are used to estimate water use from reference evapotranspiration values provided by weather stations. Two varieties of barley and durum were planted at the Maricopa Agricultural Center in late November and early January. Water use was estimated from neutron probe readings and crop coefficients were calculated by dividing water use by reference evapotranspiration. The crop coefficients calculated in this study peaked close to 1.2, similar to published values, except for the short season barley cultivar Barcott which had much lower values than the other cultivars.