Analysis of Dry-Spells in the Western Maize-Growing Areas of South Africa
Abstract
:1. Introduction
- Investigate the initial and conditional probabilities of dry- and wet-spell pentads using the Markov chain model in the western maize-growing region from mid-January to end of February;
- Determine direction and magnitude of trends of dry-spells using the Mann–Kendal monotonic trend test and the Sen slope estimator.
2. Materials and Methods
2.1. Study Area
2.2. Dataset
2.3. Data Analysis
2.3.1. Calculation of the Wet- and Dry-Spells Using the Markov Chain
2.3.2. Trend Detection Using the Mann–Kendall Test
2.3.3. Sen’s Slope Estimator
2.3.4. Spatial Analysis Interpolation
- It provides a measure of uncertainty attached to the results (i.e., Kriging variance).
- It accounts for direction-dependent relationships (i.e., spatial anisotropy).
- Weights are assigned to observations based on the spatial correlation of data instead of assumptions made by the analyst for IDW.
- Kriging predictions are not constrained to the range of observations used for interpolation.
- Data measured over different spatial supports can be combined, and change in support, such as downscaling or upscaling, can be conducted.
3. Results
3.1. Total Annual Rainfall
3.2. Dry-Spell Occurrence
3.3. Trend Analysis of Dry-Spells
4. Discussion
5. Conclusions
- An investigation into optimum planting dates by using crop models to avoid the occurrence of dry-spells should be conducted, which is crucial to assist farmers and decision makers in preventing production losses and other adverse effects of dry-spells.
- The impact of climate change on future projections of dry-spells should be investigated.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Climate Region | Climatic Properties | Vegetation | Agricultural Use |
---|---|---|---|
Dry Highveld | Temperatures often exceed 30 °C in summer months and cool during winter months, with cold nights (<5 °C) observed. Over the high-lying areas, snow does occur in winter. Precipitation ranges from about 450 to 700 mm. The rainy season reaches its peak during mid-summer in the north and late summer in the south and west. Winds tend to be from the north to north–easterly direction. | Vegetation consists of grassland with some trees along streams. | Maize production, cattle and sheep |
District | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 |
---|---|---|---|---|---|---|---|---|---|
82 | 64.5 | 58.1 | 71.0 | 80.7 | 71.0 | 54.8 | 51.6 | 64.5 | 77.4 |
83 | 67.7 | 54.8 | 54.8 | 83.9 | 67.7 | 61.3 | 61.3 | 64.5 | 80.7 |
84 | 48.4 | 41.9 | 58.1 | 77.4 | 64.5 | 61.3 | 61.3 | 48.4 | 71.0 |
85 | 41.9 | 38.7 | 64.5 | 67.7 | 77.4 | 64.5 | 71.0 | 58.1 | 80.7 |
89 | 77.4 | 67.7 | 77.4 | 77.4 | 77.4 | 71.0 | 74.2 | 64.5 | 87.1 |
90 | 71.0 | 51.6 | 64.5 | 74.2 | 67.7 | 67.7 | 58.1 | 67.7 | 83.9 |
91 | 67.7 | 48.4 | 71.0 | 74.2 | 71.0 | 64.5 | 67.7 | 58.1 | 77.4 |
92 | 54.8 | 41.9 | 64.5 | 74.2 | 61.3 | 61.3 | 64.5 | 61.3 | 83.9 |
93 | 51.6 | 61.3 | 74.2 | 74.2 | 67.7 | 64.5 | 71.0 | 74.2 | 74.2 |
District | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 |
---|---|---|---|---|---|---|---|---|---|
82 | 38.7 | 41.9 | 54.8 | 54.8 | 64.5 | 48.4 | 25.8 | 38.7 | 51.6 |
83 | 48.4 | 45.2 | 38.7 | 45.2 | 61.3 | 41.9 | 41.9 | 41.9 | 54.8 |
84 | 35.5 | 25.8 | 29.0 | 45.2 | 51.6 | 41.9 | 41.9 | 32.3 | 38.7 |
85 | 25.8 | 19.4 | 25.8 | 51.6 | 58.1 | 51.6 | 41.9 | 41.9 | 45.2 |
89 | 58.1 | 58.1 | 54.8 | 67.7 | 67.7 | 58.1 | 54.8 | 54.8 | 58.1 |
90 | 58.1 | 45.2 | 35.5 | 48.4 | 61.3 | 48.4 | 35.5 | 45.2 | 61.3 |
91 | 54.8 | 35.5 | 38.7 | 61.3 | 54.8 | 54.8 | 41.9 | 41.9 | 48.4 |
92 | 29.0 | 25.8 | 25.8 | 48.4 | 45.2 | 38.7 | 38.7 | 45.2 | 51.6 |
93 | 25.8 | 41.9 | 45.2 | 54.8 | 54.8 | 48.4 | 45.2 | 61.3 | 58.1 |
District | Dry-Spell < 15 mm | ||
---|---|---|---|
MK Stat | p-Value | Sen’s Slope | |
82 | −0.37 | 0.71 | 0 |
83 | −0.12 | 0.91 | 0 |
84 | −0.04 | 0.97 | 0 |
85 | −0.14 | 0.89 | 0 |
86 | 0.38 | 0.71 | 0 |
87 | 0.27 | 0.78 | 0 |
89 | −0.99 | 0.32 | 0 |
90 | −0.54 | 0.59 | 0 |
91 | 0.75 | 0.45 | 0 |
92 | −1.42 | 0.16 | −0.03 |
93 | 0.62 | 0.53 | 0 |
95% Confidence level—Pentads 40 to 48 (Mid-January-End of February) |
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Daniel, S.; Mengistu, M.G.; Olivier, C.; Clulow, A.D. Analysis of Dry-Spells in the Western Maize-Growing Areas of South Africa. Water 2023, 15, 1056. https://doi.org/10.3390/w15061056
Daniel S, Mengistu MG, Olivier C, Clulow AD. Analysis of Dry-Spells in the Western Maize-Growing Areas of South Africa. Water. 2023; 15(6):1056. https://doi.org/10.3390/w15061056
Chicago/Turabian StyleDaniel, Siphamandla, Michael G. Mengistu, Cobus Olivier, and Alistair D. Clulow. 2023. "Analysis of Dry-Spells in the Western Maize-Growing Areas of South Africa" Water 15, no. 6: 1056. https://doi.org/10.3390/w15061056
APA StyleDaniel, S., Mengistu, M. G., Olivier, C., & Clulow, A. D. (2023). Analysis of Dry-Spells in the Western Maize-Growing Areas of South Africa. Water, 15(6), 1056. https://doi.org/10.3390/w15061056