Soil moisture available to crops is among the main constraints on crop production by smallholder farmers in semi-arid Zimbabwe. Other restrictions, such as limited use of fertilisers and herbicides, stem primarily from socio-economic rather than biophysical constraints. To improve smallholder farming, it is essential to promote soil and water conservation practices (SWC) that consider farmers' management constraints, such as limited availability of labour and Draught Animal Power (DAP).

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No description available.

Drought is a water related natural hazard. It is difficult to characterize drought because of its diffused nature and spatiotemporal variability. However, understanding the variability of drought characteristics such as severity, frequency, duration, and spatial extent is critical in drought mitigation and planning. Impact of drought on agriculture, water supply, and energy sectors has been long-recognized. The current understanding of drought and its impact is limited due to its complex characteristics and ways in which it impacts various sectors. This study focuses on two important aspects of drought: variability of drought characteristics across different spatial scales, and impact of droughts on crop yield and groundwater. Two drought indices, one integrating severity and spatial coverage, and also taking into account the type of specific crops, were investigated for county level use. The developed indices were used in studying drought at the county level, and its impact on crop yields. These indices can be used for resource allocation at the county level for drought management. Drought is reported in the United States (U.S.) for different administrative units at different spatial scales. The variation of drought characteristics across different spatial scales and scale dependence was investigated, demonstrating the importance of considering spatial scales in drought management. A methodology is proposed to quantify the uncertainty in reported values of drought indices using geostatistical tools. The uncertainty was found to increase with increasing spatial scale size. Artificial Neural Network and regression methods were used to model the impact of drought on crop yield and groundwater resources. Relationships of crop yields and groundwater levels with drought indices were obtained. Overall, this study contributes towards understanding of the spatial variation of drought characteristics across different spatial scales, and the impact of drought on crop yields and groundwater levels. / North Dakota Water Recourses Research Institute (ND WRRI) Fellowship Program / North Dakota State University Graduate School Doctoral Dissertation Award

Municipal water suppliers are increasingly faced with implementing programs to address temporary water shortages in the United States. Having reliable estimates for the effectiveness of these programs will help in water supply planning. This dissertation estimates the reductions in residential water-use for voluntary and mandatory water-use restrictions used in Virginia during the 2002 drought. These restrictions were evaluated using both a conventional approach (single-dummy variable for each) and non-conventional approach where program intensity was accounted for. Program intensity was measured by information dissemination for voluntary restrictions, and by information dissemination and enforcement efforts for mandatory restrictions. An unbalanced panel with data from 21 municipal water suppliers was used in the analysis. Under the conventional approach, voluntary restrictions had no significant effect on water-use and mandatory restrictions showed a small to moderate effect. However, program intensity was found to have a significant influence on the magnitude of the water-use reductions in the non-conventional approach. These reductions ranged from 0-7% for voluntary restrictions, and from 0-22% for mandatory restrictions. Moreover, these reductions followed a pattern of increasing program effectiveness with higher levels of information and enforcement. This result indicates that water supply planners need to give considerable attention to the manner in which drought management programs are implemented. Price was also found to have an important effect on residential water-use. A moderate price increase of $3 per 1000 gallons would be expected to reduce water-use by almost 15%. Thus combining mandatory restrictions (implemented at high intensity) with a moderate to high price increase could result in water-use savings approaching 40% based on estimates from this analysis. Other important findings included: a) consumers were responding to a mix of pure marginal price and fixed fees/previous block rates, b) apartment accounts were found to be included in most of the localities residential data and had a significant impact on water-use, and c) the income parameter was measuring more than a pure income effect. / Ph. D.

Summaries in English, Afrikaans and Sepedi / The Limpopo Province is a disaster-prone province, with drought being the most common natural disaster. From the year 2012 onwards, the province experienced extremely dry conditions that culminated in a severe drought in 2016. This negatively impacted the livelihoods of smallholder livestock farmers and the welfare of their livestock. The study investigated the coping strategies that were adopted by smallholder livestock farmers during drought conditions and the factors that were associated with animal loss during the drought that affected the region between 2014 and 2016. A randomly selected sample of 281 smallholder livestock farmers aged 18 years and older from the Greater Letaba Local Municipality participated in the study. Structured interviews, aided by questionnaires were used to collect the primary data. Proportions of categorical variables and the mean and standard deviation for continuous variables were computed and presented as tables and figures. A Poisson regression model was fitted to the data to identify factors that were significantly associated with loss of animals during the drought. More than half (55.50%; n=116) of the participants were made aware of the 2014–2016 drought through the agricultural extension officers, followed by 19.14% (n=40) who got to know about it through radio channels. More than half of the participants (58.29%; n=123) were aware of the impending drought. The most common support received from government agencies to help cope with the drought was in the form of animal feed (80%; n=124). Although most of the farmers (73.55%; n=114) benefitted from the support they received, slightly more than half (53.74%; n=151) did not cope well with the drought conditions. While Bellevue (B=-0.199; 95% CI: -0.380 -0.019) was negatively associated with loss of animals, Mokwakwaila (B=0.568; 95% CI: 0.405 0.731) had a strong positive association with loss of animals. Being married (B=-0.060; 95% CI: -0.305 0.183) or divorced (B= -0.035; 95% CI: -0.316 0.246) was negatively associated with loss of animals. Years of experience in farming (B=0.022; 95% CI: 0.010 0.033) and not receiving support during were strongly positively associated with loss of animals (B=0.324; 95% CI: 0.189 0.459). The low number of farmers who were aware of the impending drought and the large number of farmers who did not cope well suggests that many farmers in the area were not prepared for the drought. Groups such as widows, widowers and farmers who have many years of farming experience are high-risk groups and should be targeted for interventions in the event of a drought. More measures are needed to ensure that all agricultural centres are prepared and supported in event of a drought so as to minimise the impact of drought on local communities. / Die provinsie Limpopo is 'n rampgevoelige provinsie, met droogte as die mees algemene natuurramp. Vanaf 2012 het die provinsie uiters droë toestande beleef wat in 2016 op 'n ernstige droogte uitgeloop het. Dit het 'n negatiewe uitwerking gehad op die lewensonderhoud van kleinboere en die welstand van hul vee. Die studie het ondersoek ingestel na die hanteringstrategieë wat deur veeboere in kleinvee tydens droogtetoestande aangeneem is, en die faktore wat verband hou met diereverlies tydens die droogte wat die streek tussen 2014 en 2016 geraak het. 'N Lukraak geselekteerde steekproef van 281 kleinboere van 18 jaar en ouer van die Greater Letaba Local Munisipaliteit het aan die studie deelgeneem. Gestruktureerde onderhoude, gehelp deur vraelyste, is gebruik om die primêre data in te samel. Verhoudings van kategoriese veranderlikes en die gemiddelde en standaardafwyking vir deurlopende veranderlikes is bereken en as tabelle en figure aangebied. 'N Poisson-regressiemodel is op die data toegepas om faktore te identifiseer wat beduidend verband hou met die verlies aan diere tydens die droogte. Meer as die helfte (55,50%; n=116) van die deelnemers is bewus gemaak van die droogte 2014–2016 deur die landbouvoorligtingsbeamptes, gevolg deur 19,14% (n =40) wat dit via radiokanale leer ken het. Meer as die helfte van die deelnemers (58,29%; n=123) was bewus van die dreigende droogte. Die mees algemene steun van regeringsinstansies om die droogte die hoof te bied, was in die vorm van veevoer (80%; n=124). Alhoewel die meerderheid van die boere (73,55%; n=114) voordeel getrek het uit die steun wat hulle gekry het, het die droogtetoestande nie goed hanteer nie (53,74%; n=151). Terwyl Bellevue (B= -0.199; 95% CI -0.380 -0.019) negatief geassosieer is met verlies aan diere, is Mokwakwaila (B= 0,568; 95% CI 0,405 0,731) sterk positief geassosieer met verlies aan diere. Om getroud te wees (B= -0.060; 95% CI -0.305 0.183) of geskei (B= -0.035; 95% CI 0.316 0.246) was negatief geassosieer met verlies aan diere. Jare se ondervinding in die boerdery (B=0,022; 95% CI 0,010 0,033) en om nie ondersteuning gedurende te ontvang nie, was sterk positief geassosieer met die verlies van diere (B=0.324; 95% CI 0.189 0.459). Die lae aantal boere (ongeveer die helfte) wat bewus was van die dreigende droogte, dui daarop dat baie boere in die omgewing nie voorbereid was op die droogte nie. Groepe soos weduwees, wewenaars en boere met baie jare se boerdery-ervaring, is hoërisikogroepe en moet geteiken word vir ingrypings in die geval van 'n droogte. Meer maatreëls is nodig om te verseker dat alle landbousentrums voorberei en ondersteun word in geval van 'n droogte om die impak van droogte op plaaslike gemeenskappe te verminder. / Komelelo ke bothata bjo bogolo kudu go tsa temo/bolemi, segolothata re lebeletse balemirui ba bannyane. Limpopo province e na le kgatelelego ye kgolo kudu ka komelelo gagolo ge re lebeletse tsa bolemi. Nako le nako komelelo e tsea karolo ye kgolo moo e feleletsago e gatelela tsa temo. Tabakgolo ya rena kego lebelela ditsela le mehuta ye e fapanego yeo e shomishitshwego ke balemi go lwantshana le bothata bja komelelo gareng ga ngwaga wa 2014- 2016. Thuto ye e kgobokantshitshwe gotwsa go masepala wa motse selegae wa Greater Letaba Local Municipality, karolo ya Mopani, profenseng ya Leboa mo Afrika Borwa. Tshedimosho ye e hweditshwe ka mokgwa wa poledisano le balemi bao ba fapanego ba go lekana nomoro ya 281 ya balemi go dinaga tsa go fapanafapana. Poledisano ebile ka mokgwa wa peakanyanyo ya dopotsisho. Tshedimosho ye e kopantshitshwe le go hlathollwa ka mokgwa wa go ikgetha wa Strata Version 14. Hlathollo ya go ikgetha e berekishitshwe ka mokgwa wa ditiragalo yoya ka nako le dipalopalo tsa go kopantswa fao tahlegelo e sa tsebjego go ka lekanywa.le bokae la diperesente. Mabakakgolo ao a hlolago tahlegelo ya diruiwa a nyakishitswe ka mokgwa wa Poisson Regression Model. Bogolo bja (64.77%) go bao ba arabilego ebile banna le bogolo bja (74.38%) bja balemi ba be ba tseba ka komelelo ye e batamelago. Go feta halofo (55.50%) ya bao ba arabilegoba tsebishitshwe ka komelelo yeo e batamelang go tswa go bagakolodi, gomme gwa latela thelebisheni (8.13%) le dikuranta (1.44%). Go feta bogolo bja (58.29%) bja bao ba ikarabetsego ba laeditswe gore ba be ba tseba ka komelelo yeo e batamelago ke fao ba bego ba ikemiseditse. Bontshi bja thekgo (80%) yeo balemi ba e hweditsego ebile ka mokgwa wa dijo tsa diphoofolo, gwa latela latela thekgo yeo e filwego ka mokgwa wa meets le dithibela malwetsi go diphoofolo. Bogolo bjago makatsa (73.55%) bo laeditse gore thekgo yeo ba e hweditsego e ba tshwetsi molemo le diphoofolo tsa bona, go feta bonnyane (26.45%) bjoo bo rilego thekgo yeo ba e hweditsegobka nako ya komelelo ga se ya ba tshwela mohola goba gaya ba hola ka selo. Go ba modudi wa Bellevue (B= -0.199; 95% CI: -0.380 -0.019, p= 0.031) le Mokwakwaila (B=0.568; 95% CI: 0.405 0.731, p= 0.0001) ebile nthla ye bohlokwa go tahlegelo ya dirui. Go oketsa seo, go nyadiwa (B=0.942; 95% CI: 0.737 1.201), go hladiwa (B= 0.966 (95% CI: 0.729 1.279), le palo ya mengwaga ya botsebingo tsa temo (B=1.022; 95% CI: 1.010 1.034, p= 0.0001), le ge eba molemi ga se a hwetse thusho ka nako ya komelelo (B=0.324; 95% CI: 0.189 0.459, p= 0.0001) ebile dinhla tsa bohlokwa go tahlegelo ya dirui ka nako ya komelelo. Palo ya fase ba balemi bao ba bego bas a tsebe ka komelelo yeo e bego e batamela, e kgathile tema ye kgolo mo tabeng ya go paledisha balemi go ipeakanyela kgahlanong le komelelo yeo e bego e batamela. Ka fao seo se ba amile gampe. Mo nakong ye e tlang, matsapa a mantsi a swanetswi go tseiwa go kgonthishisha gore tsa temo ka moka di itokishetsa ka go lekana. Mmusho o swanetse go beeletsa kudu go lefapha la bagakolodi ka go oketsa palo ya mafapha a bagakolodi. / Agriculture and Environmental Sciences / M.Sc. (Agriculture)

abstract: The phrase water-energy nexus is commonly used to describe the inherent and critical interdependencies between the electric power system and the water supply systems (WSS). The key interdependencies between the two systems are the power plant’s requirement of water for the cooling cycle and the water system’s need of electricity for pumping for water supply. While previous work has considered the dependency of WSS on the electrical power, this work incorporates into an optimization-simulation framework, consideration of the impact of short and long-term limited availability of water and/or electrical energy. This research focuses on the water supply system (WSS) facet of the multi-faceted optimization and control mechanism developed for an integrated water – energy nexus system under U.S. National Science Foundation (NSF) project 029013-0010 CRISP Type 2 – Resilient cyber-enabled electric energy and water infrastructures modeling and control under extreme mega drought scenarios. A water supply system (WSS) conveys water from sources (such as lakes, rivers, dams etc.) to the treatment plants and then to users via the water distribution systems (WDS) and/or water supply canal systems (WSCS). Optimization-simulation methodologies are developed for the real-time operation of water supply systems (WSS) under critical conditions of limited electrical energy and/or water availability due to emergencies such as extreme drought conditions, electric grid failure, and other severe conditions including natural and manmade disasters. The coupling between WSS and the power system was done through alternatively exchanging data between the power system and WSS simulations via a program control overlay developed in python. A new methodology for WDS infrastructural-operational resilience (IOR) computation was developed as a part of this research to assess the real-time performance of the WDS under emergency conditions. The methodology combines operational resilience and component level infrastructural robustness to provide a comprehensive performance assessment tool. The optimization-simulation and resilience computation methodologies developed were tested for both hypothetical and real example WDS and WSCS, with results depicting improved resilience for operations of the WSS under normal and emergency conditions. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

Un sistema de gestión de sequías apropiado requiere de la anticipación de los posibles efectos que un episodio de este tipo tenga sobre el sistema de recursos hídricos. Esta tarea sin embargo resulta más complicada de lo que parece. En primer lugar, debido al alto grado de incertidumbre existente en la predicción de variables hidrológicas futuras. Y en segundo, debido al riesgo de sobrerreacción en la activación de medidas de mitigación generando falsa sensación de escasez, o sequía artificial. A este respecto, los planes especiales de sequía proveen de herramientas para la gestión eficiente de situaciones con escasez de recursos y la preparación de cara a futuros eventos. De todos modos, las diferentes estrategias de operación seguidas en cada sistema de recursos hídricos hacen que las herramientas que en algunos casos resultaron altamente útiles no lo sean tanto cuando se aplican en sistemas distintos. Debido a la falta de tiempo y/o al exceso de confianza en los trabajos realizados por terceros, con excelentes resultados en sus respectivos casos, a veces se cae en el error de implementar metodologías no del todo apropiadas en sistemas con requisitos completamente distintos. El desarrollo y utilización de metodologías generalizadas aplicables a diferentes sistemas y capaces de proporcionar resultados adaptados a cada caso es, por tanto, muy deseable. Este es el caso de las herramientas de modelación de sistemas de recursos hídricos generalizadas. Estas permiten homogeneizar los procesos mientras siguen siendo los suficientemente adaptables para proporcionar resultados apropiados para cada caso de estudio. Esta tesis presenta una serie de herramientas destinadas a avanzar en el análisis y comprensión de los sistemas de recursos hídricos, haciendo énfasis en la prevención de sequías y la gestión de riesgos. Las herramientas desarrolladas incluyen: un modelo de optimización generalizado para esquemas de recursos hídricos, con capacidad para la representación detallada de cualquier sistema de recursos hídricos, y una metodología de análisis de riesgo basada en la optimización de Monte Carlo con múltiples series sintéticas. Con estas herramientas es posible incluir tanto la componente superficial como la subterránea del sistema estudiado dentro del proceso de optimización. La optimización está basada en la resolución iterativa de redes de flujo. Se probó la consistencia y eficiencia de diferentes algoritmos de resolución para encontrar un balance entre la velocidad de cálculo, el número de iteraciones, y la consistencia de los resultados, aportando recomendaciones para el uso de cada algoritmo dadas las diferencias entre los mismos. Las herramientas desarrolladas se aplican en dos casos de estudio reales en la evaluación y posibilidad de complementación de los sistemas de monitorización y alerta temprana de sequías existentes en los mismos. En el primer caso, se propone un enfoque alternativo para la monitorización de la sequía en el sistema de operación anual del río Órbigo (España), complementándolo con la utilización de la metodología de análisis de riesgo. En el segundo caso, las herramientas se emplean en un sistema con una estrategia de operación completamente distinta. Se estudia como el análisis de riesgo de la gestión óptima puede ayudar a la activación anticipada de los escenarios de sequía en los sistemas de los ríos Júcar y Turia, cuya operación es hiperanual. En esta ocasión, el sistema de indicadores existente goza de una gran confianza por parte de los usuarios. La metodología de análisis de riesgo es, sin embargo, capaz de anticipar los eventos de sequía con mayor alarma, aspecto que es deseable si se quiere evitar que los episodios en desarrollo vayan a más. En ambos casos se muestra como la evaluación anticipada de las posibles situaciones futuras del sistema permiten una definición confiable de los escenarios de sequía con suficiente antelación para la activación efectiva de medidas de prevención y/o mitigación en caso de ser necesarias. La utilización de indicadores provenientes de modelos frente a indicadores basados en datos observados es complementaria y ambos deberían utilizarse de forma conjunta para mejorar la gestión preventiva de los sistemas de recursos hídricos. El empleo de modelos de optimización en situaciones de incertidumbre hidrológica es muy apropiado gracias a la no necesidad de definir reglas de gestión para obtener los mejores resultados del sistema, y teniendo en cuenta que las reglas de operación habituales pueden no ser completamente adecuadas en estas ocasiones. / Haro Monteagudo, D. (2014). Methodology for the optimal management design of water resources system under hydrologic uncertainty [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/45996 / TESIS

Recurring drought conditions have always been an endemic feature of climate in South Africa, limiting maize development and production. However, recent projections of the future climate by the Intergovernmental Panel on Climate Change suggest that due to an increase of atmospheric greenhouse gases, the frequency and severity of droughts will increase in drought-prone areas, mostly in subtropical climates. This has raised major concern for the agricultural sector, particularly the vulnerable small-scale farmers who merely rely on rain for crop production. Farmers in the Luvuvhu River catchment are not an exception, as this area is considered economically poor, whereby a significant number of people are dependent on rain-fed farming for subsistence. This study was therefore conducted in order to improve agricultural productivity in the area and thus help in the development of measures to secure livelihoods of those vulnerable small-scale farmers. Two drought indices viz. Standardized Precipitation Evapotranspiration Index (SPEI) and Water Requirement Satisfaction Index (WRSI) were used to quantify drought. A 120-day maturing maize crop was considered and three consecutive planting dates were staggered based on the average start of the rainy season. Frequencies and probabilities during each growing stage of maize were calculated based on the results of the two indices. Temporal variations of drought severity from 1975 to 2015 were evaluated and trends were analyzed using the non-parametric Spearman’s Rank Correlation test at α (0.05) significance level. For assessing climate change impact on droughts, SPEI and WRSI were computed using an output from downscaled projections of CSIRO Mark3.5 under the SRES A2 emission scenario for the period 1980/81 – 2099/100. The frequency of drought was calculated and the difference of SPEI and WRSI means between future climate periods and the base period were assessed using the independent t-test at α (0.10) significance level in STATISTICA software. The study revealed that planting a 120-day maturing maize crop in December would pose a high risk of frequent severe-extreme droughts during the flowering to the grain-filling stage at Levubu, Lwamondo, Thohoyandou, and Tshiombo; while planting in October could place crops at a lower risk of reduced yield and even total crop failure. In contrast, stations located in the low-lying plains of the catchment (Punda Maria, Sigonde, and Pafuri) were exposed to frequent moderate droughts following planting in October, with favorable conditions noted following the December planting date. Further analysis on the performance of the crop under various drought conditions revealed that WRSI values corresponding to more intense drought conditions were detected during the December planting date for all stations. Moreover, at Punda Maria, Sigonde and Pafuri, it was observed that extreme drought (WRSI <50) occurred once in five seasons, regardless of the planting date. Temporal analysis on historical droughts in the area indicated that there had been eight agricultural seasons subjected to extreme widespread droughts resulting in total crop failure i.e. 1983/84, 1988/89, 1991/92, 1993/94, 2001/02, 2002/03, 2004/05 and 2014/15. Results of Spearman’s rank correlation test revealed weak increasing drought trends at Thohoyandou (ρ = of 0.5 for WRSI) and at Levubu and Lwamondo (ρ = of 0.4 for SPEI), with no significant trends at the other stations. The study further revealed that climate change would enhance the severity of drought across the catchment. This was statistically significant (at 10% significance level) for the near-future and intermediate-future climates, relative to the base period. Drought remains a threat to rain-fed maize production in the Luvuvhu River catchment area of South Africa. In order to mitigate the possible effects of droughts under climate change, optimal planting dates were recommended for each region. The use of seasonal forecasts during drought seasons would also be useful for local rain-fed maize growers especially in regions where moisture is available for a short period during the growing season. It was further recommended that the Government ensure proper support such as effective early warning systems and inputs to the farmers. Moreover, essential communication between scientists, decision makers, and the farmers can help in planning and decision making ahead of and during the occurrence of droughts. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)