Estimation of small reservoir storage capacities in Limpopo River Basin using geographical information systems (GIS) and remotely sensed surface areas: case of Mzingwane catchment

The current interest in small reservoirs stems mainly from their utilization for domestic use, livestock watering, fishing and irrigation. Rarely were small reservoirs considered in the water resources system even though they are important in water resource planning and management. The main limitation being lack of knowledge on small reservoir capacities, for the methodologies used to quantify physical parameters of reservoirs are costly, time consuming and laborious. To address this challenge an attempt has been made in this study to estimate small reservoir storage capacities using remotely sensed surface areas. A field study on 12 small reservoirs was carried out in Mzingwane catchment in Limpopo River Basin; Zimbabwe. The depths of water accompanied with their coordinates were measured; from which area and capacity were calculated for each reservoir using geographical information system based on data acquired from the field and that from satellite images. The output data was compared and a linear regression analysis was carried out to establish a power relationship between surface area and storage capacity of small reservoirs. The Pearson correlation analysis at 95% confidence interval indicated that the variances of the two surface areas (field area and image area) were not significantly different (p < 0.05). The findings from linear regression analysis (log capacity–log area) show that there exist a power relationship between remotely sensed surface areas (m^2) and storage capacities of reservoirs (m^3), with 95% variation of the storage capacity being explained by surface areas. The relationship can be used as a tool in decision-making processes in integrated water resources planning and management in the river basin. The applicability of the relationship to other catchments requires further research as well as investigating the impacts of small reservoirs in water resources available in the river basin by carrying out a hydrological modelling of the catchment

Evaluation of FAO AquaCrop Model for ability to simulate attainable yields and water use for field tomatoes grown under deficit irrigation in Harare, Zimbabwe

Crop simulation models have an important role in evaluating irrigation management strategies for improving agricultural water use. The aim of this study was to evaluate the AquaCrop model for ability to simulate water use and tomato (Lycopersicon esculentum Mill.) fruit yields under deficit irrigation conditions. A fieldexperiment was conducted at Thornpark, University of Zimbabwe Research site over four seasons (2014 and 2017). The data collected for yield and water use were used to run and evaluate the performance of AquaCrop in predicting water use efficiency and fruit yield. Four treatments defined in relation to 100% of the crop water requirement (ETc) were simulated: T1 100% ETc; T2 80% ETc; T3 60% ETc and T4 50% ETc. The model performance was satisfactory, with a good correlation between the simulated and observed soil water content (SWC) and fruit yield (FY). All the statistical indicators (The Normalised Root Mean Square Error (R2), Root Mean Square Error (RMSE), Nush Sutcliffe Model Efficiency (EF), Pearson Correlation Coefficient (r), and Willmott’s Index of Agreement (d)) used to compare the observed and predicted parameters, showed good performance; for example the EF showed values of 0.91 for SWC, the (r) showed values of 0.95 for SWC and a FY of 2.79 and 2.39 metric tonnes ha-1 for the simulated results. The results showed that the values of the simulated FY were consistent with the measured, with corresponding coefficients of determination (R2) of 0.93. The results revealed AquaCropisable to simulate the yield of tomato and the seasonal water requirements to an appreciable degree. However, it must be pointed out that the calibration of AquaCrop suffered from lack of measured data on the progress of crop canopy cover, which is an important parameter used in developing the model. The results obtained showed that AquaCrop can be used effectively in simulating tomato production under deficit irrigation and, therefore, it can be used as a decision-making tool for irrigation management of tomatoes in Zimbabwe

Use of the FAO AquaCrop model in developing sowing guidelines for rainfed maize in Zimbabwe

This paper presents a procedure in which the water-driven water productivity model AquaCrop was fine-tuned and validated for maize for the local conditions in Zimbabwe and then applied to develop sowing management options for decision support. Data from experiments of 2 seasons in Harare and from 5 other sites around Zimbabwe were used for the local calibration and validation of AquaCrop. Model parameters such as the reference harvest index (HIo); the canopy growth coefficient (CGC); early canopy decline and normalised biomass water productivity (WPb*) were adjusted during model calibration. Model performance was satisfactory after calibration with a Nash-Sutcliffe model efficiency parameter (EF = 0.81), RMSE = 15% and R2 = 0.86 upon validation. To develop sowing guidelines, historical climate series from 13 meteorological stations around Zimbabwe were used to simulate maize yield for 6 consecutive sowing dates determined according to criteria applicable in Zimbabwe. Three varieties and typical shallow and deep soil types were considered in the simulation scenarios. The simulated yield was analysed by an optimisation procedure to select the optimum sowing time that maximised long-term mean yield. Results showed that highest yields depended on the climate of the site (rainfall availability), variety (length of growing cycle) and soil depth (soil water storage capacity). The late variety gave higher mean yields for all sowing dates in the maize belt. Staggered sowing is recommended as a way of combating the effects of rainfall variability and as an answer to labour constraints.Keywords: biomass water productivity, AquaCrop, maize sowing dates, crop modellin

Relative transpiration as a decision tool in crop management: a case for rainfed maize in Zimbabwe

Water stress has been considered to be the primary constraint to yield in water-limited arid and semi-arid environments. This paper describes the characterisation of the rainfall season using relative transpiration (Trel) of a maize crop at 13 climate stations in Zimbabwe. A soil water balance model was used to simulate relative crop transpiration for a maize crop over the duration of each rainfall season to assess its quality (severity of intraseasonal dry spells). The Trel and length of growing period (LGP) were subjected to frequency analyses and the results were interpolated (kriging) to form a GIS library of expected events in normal, wet and dry years. The normal LGP (50% PE) varied across the stations, with a range of 75 days, exposing opportunities for objective management of variety selection to match crop growth cycles to expected LGP. The time series of Trel showed the time variation of quality of the season with periods of high Trel identifying the high quality parts of the rainfall season suitable for crop production. Soil depth influenced quality of the season, with deeper soils improving quality. A simple tool that can be used to indicate whether or not to grow maize varieties of particular length of growth cycle in a specified region for typical wet, normal or dry rainfall seasons was developed.Le stress hydrique a \ue9t\ue9 consid\ue9r\ue9 comme contrainte majeure au rendement des cultures dans en r\ue9gions arides et semi arides. Cet articles decrit la caract\ue9risation de la saison pluviom\ue9trique par la transpiration relative (Trel) de la culture de ma\ubfs dans 13 stations climatiques au Zimbabwe. Un mod\ue8le de balance sol-eau \ue9tait utilis\ue9 pour simuler la transpiration relative pour la culture du ma\ubfs sur une dur\ue9e de chaque saison de pluie pour \ue9valuer sa qualit\ue9 (s\ue9verit\ue9 entre les saisons s\ue8ches). La Trel et la longueur de la p\ue9riode de croissance \ue9taient soumises aux analyses de fr\ue9quence et les r\ue9sultats \ue9taient interpoll\ue9s (kriging) pour former une base des donn\ue9es GIS des \ue9v\ue9nements attendus des ann\ue9es normales aussi bien que humides que s\ue8ches. Le LGP normal (50% PR) variait \ue0 travers les stations, avec environ 75 jours, r\ue9v\ue9lant des opportunit\ue9s pour une gestion objective de la s\ue9lection vari\ue9tale, afin de correspondre les cycles de croissance au LGP attendu. Le temps de s\ue9rie de la Trel a montr\ue9 la variation dans le temps de la qualit\ue9 de la saison des p\ue9riodes de Trel \ue9lev\ue9e identifiant les parties de haute qualit\ue9 de la saison pluvieuse appropri\ue9es \ue0 la production des cultures. La profondeur du sol a influenc\ue9e la qualit\ue9 de la saison, avec des qualit\ue9s am\ue9liorant les sols les plus profonds. Un simple outil qui peut \ueatre utilis\ue9 pour produire ou pas des vari\ue9t\ue9s de ma\ubfs d\u2019un cycle particulier de longueur de croissance dans une r\ue9gion sp\ue9cifi\ue9e pour des saisons \ue0 pr\ue9cipitation typiquement humide, normale ou s\ue8che \ue9tait d\ue9velopp\ue

Home-administered pre-surgical psychological intervention for knee osteoarthritis (HAPPiKNEES): study protocol for a randomised controlled trial

Background: Knee replacement surgery reduces pain for many people with osteoarthritis (OA). However, surgical outcomes are partly dependent on patients’ moods, and those with depression or anxiety have worse outcomes. Approximately one-third of people with OA have mood problems. Cognitive behavioural therapy (CBT), a psychological therapy, is recommended by the National Institute for Health and Care Excellence for improving mood. However, evidence for the effectiveness of CBT before knee surgery in improving pain, mood, and quality of life following this surgery for people with knee OA is lacking. Methods/Design: This is a multi-centre, mixed-methods feasibility randomised controlled trial to compare treatment as usual (TAU) plus a brief CBT-based intervention with a TAU-only control, for people with knee OA. We will recruit 50 patients with knee OA, listed for knee replacement surgery, with high levels of distress (assessed using a mood questionnaire), and who consent to take part. Participants will be randomly allocated to receive TAU plus intervention or TAU. Up to 10 sessions of CBT will be offered on an individual basis by a psychologist. The assessments and interventions will be completed before surgery. Repeat assessments at 4 and 6 months after randomisation will be sent and received by post. Two patient-partners will conduct feedback interviews with some participants to assess what aspects of the intervention were helpful or unhelpful, the acceptability of randomisation, the experience of being in a control group, and the appropriateness of the measures used. Interviews will be audio-recorded, transcribed, and analysed using the framework approach. We will examine the feasibility and acceptability of patient-partners conducting the interviews by also interviewing the patient-partners. Discussion: Findings from this study will be used to design a definitive study that will examine the clinical and cost-effectiveness of the CBT intervention in improving patient outcomes following knee surgery

Resilience Pathways for Schooling Reunified Former Street Children in Harare

The present study sought to explore the resilience pathways for school engagement among reunified former street children in Harare. In order to explore such resilience, the study employed a qualitative approach of phenomenology. The study was based on the social ecological theory of resilience. Data were collected using semi-structured interviews. A total of 14 reunified former street children aged between 11 and 18 participated in the current study. Purposive sampling was employed to recruit participants for this research. Data was analysed using the interpretive phenomenological analysis. Data analysis revealed the resilience pathways, including substance use, peer relationships, having role models, religious practices, psychological capital, family members, changing residence, intimate relationships and availability of sponsors. The authors recommend resilience promoting strategies for such reunified former street children including equipping them with vocational and life skills, ensure thorough family tracing and reunification, together with rehabilitation of the children and counselling of their guardians. In addition, responsible authorities such as the Department of Social Services together with other stakeholders in the community should also assist parents and guardians with appropriate parenting skills

MODEL PREDICTION OF MAIZE YIELD RESPONSES TO CLIMATE CHANGE IN NORTH-EASTERN ZIMBABWE

The increasing frequency and severity of droughts and floods, the shift in onset of the rains, increasing intensity of mid-season wet and dry spells and variations in the cessation of the rains in the last 50 years have been identified in the Intergovernmental Panel on Climate Change Third Assessment Report (IPCC-TAR) as a major consequence of climate change. This paper presents a study that was conducted to project climatic trends in Zimbabwe by the end of the 21st Century. observed data of the last three decades (1971 to 2000) from several climatological stations in north-eastern Zimbabwe and outputs from several global climate models were used. The downscaled model simulations consistently predicted a warming of between 1 and 2 ºC above the baseline period (1971-2000) at most of the stations in the period 2046-2065. Most of the models predicted that for the same period, rainfall will decrease by an average of 10 mm for each month for october to December; while there will be an average increase of 10 mm for the months of January to April. The AquaCrop crop production model simulations predicted that climate change will shift planting dates towards delayed planting in the period 2O46- 2O65. The results further showed that using traditional static sowing practices in the period 2O46-2O65 will result in maize ( Zea mays L.) yield reductions, while adopting dynamic planting strategies will result in highest maize yields for short season cultivars.La fréquence sans cesse croissante et la gravité des sécheresses et inondations, le changement dans l’apparition des pluies, l’intensité croissante de la mi-saison humide et la sécheresse ainsi que les variations dans la cessation des pluies au cours des 50 dernières années, ont été identifiées comme étant une conséquence majeur du changement climatique dans le Panel intergouvernemental du troisième rapport d’évaluation (PICC-TAR) du changement climatique. Cet article présente une étude conduite pour projeter les tendances climatiques au Zimbabwe à la fin du 21e siècle. Les données des trois dernières décennies (1971-2000) dans plusieurs stations climatologiques au Nord-Est du Zimbabwe et les résultats de plusieurs modèles climatiques du Globe étaient utilisées. Les modèles de simulation à échelle réduite ont avec consistance prédit un réchauffement d’entre 1 et 2 ºC au-dessus de la période de référence (1971-2000) dans la plupart des stations pour la période 2046-2065. La plupart des modèles ont prédit que pour la même période, les précipitations diminueront en moyenne de 10 mm pour chaque mois d’octobre à Décembre, alors qu’il y aura une augmentation moyenne de 10 mm pour les mois de Janvier à Avril. Les modèles de simulation AquaCrop pour la production agricole ont prédit que le changement climatique entrainera le retard dans les dates de plantation au cours des années 2O46-2O65. Les résultats ont en plus montré que par l’utilisation des pratiques traditionnelles statiques de plantation dans la période 2O46-2O65, la culture du maïs ( Zea mays L.) connaîtra une réduction du rendement alors que adoption des stratégies dynamiques de plantation entrainera des rendements les plus élevés du maïs pour les cultivars de courtes saisons

Citrus crop water requirements in northern Zimbabwe: significance of the whole season irrigation calendar

This study, carried out at Mazowe Citrus Estate, was aimed at developing drip irrigation guidelines for citrus in northern Zimbabwe in the form of irrigation calendars throughout the season. In order to achieve this, an automatic weather station was used to obtain the average ETo values for the study site which were derived from micro climatic data. The ETo trend for the study site was established from the FAO Penman Monteith equation using observed and historical climatic data. BUDGET (version 6.2), a soil water balance model was used to develop irrigation calendars using a fixed irrigation interval of one day. The irrigation calendars presents irrigation depths linked to the actual weather conditions throughout the season. The model was also used to simulate the soil water status after using the irrigation guidelines. The developed irrigation guidelines were compared with the grower's scheduling practise. There is a possibility that the grower was over irrigating based on simulated soil moisture conditions usually above the field capacity. High drainage losses of up to 1964 mm for the whole season were simulated compared to 381 mm for the irrigation scheduling guidelines. The grower s irrigation depths were found to be too high and therefore not compatible with a 1 day irrigation interval. Almost a third of the current irrigation depth was required under normal weather conditions. The excessive application of water might be associated with high drainage losses. Irrigation depth was reduced after considering the developed irrigation calendars. Taking into account the atmosphere's evaporative demand (the actual weather condition of the day) is an effective way of irrigation scheduling

Relative transpiration as a decision tool in crop management: a case for rainfed maize in Zimbabwe

Water stress has been considered to be the primary constraint to yield in water-limited arid and semi-arid environments. This paper describes the characterisation of the rainfall season using relative transpiration (Trel) of a maize crop at 13 climate stations in Zimbabwe. A soil water balance model was used to simulate relative crop transpiration for a maize crop over the duration of each rainfall season to assess its quality (severity of intraseasonal dry spells). The Trel and length of growing period (LGP) were subjected to frequency analyses and the results were interpolated (kriging) to form a GIS library of expected events in normal, wet and dry years. The normal LGP (50% PE) varied across the stations, with a range of 75 days, exposing opportunities for objective management of variety selection to match crop growth cycles to expected LGP. The time series of Trel showed the time variation of quality of the season with periods of high Trel identifying the high quality parts of the rainfall season suitable for crop production. Soil depth influenced quality of the season, with deeper soils improving quality. A simple tool that can be used to indicate whether or not to grow maize varieties of particular length of growth cycle in a specified region for typical wet, normal or dry rainfall seasons was developed.Le stress hydrique a été considéré comme contrainte majeure au rendement des cultures dans en régions arides et semi arides. Cet articles decrit la caractérisation de la saison pluviométrique par la transpiration relative (Trel) de la culture de ma¿s dans 13 stations climatiques au Zimbabwe. Un modèle de balance sol-eau était utilisé pour simuler la transpiration relative pour la culture du ma¿s sur une durée de chaque saison de pluie pour évaluer sa qualité (séverité entre les saisons sèches). La Trel et la longueur de la période de croissance étaient soumises aux analyses de fréquence et les résultats étaient interpollés (kriging) pour former une base des données GIS des événements attendus des années normales aussi bien que humides que sèches. Le LGP normal (50% PR) variait à travers les stations, avec environ 75 jours, révélant des opportunités pour une gestion objective de la sélection variétale, afin de correspondre les cycles de croissance au LGP attendu. Le temps de série de la Trel a montré la variation dans le temps de la qualité de la saison des périodes de Trel élevée identifiant les parties de haute qualité de la saison pluvieuse appropriées à la production des cultures. La profondeur du sol a influencée la qualité de la saison, avec des qualités améliorant les sols les plus profonds. Un simple outil qui peut être utilisé pour produire ou pas des variétés de ma¿s d’un cycle particulier de longueur de croissance dans une région spécifiée pour des saisons à précipitation typiquement humide, normale ou sèche était développ