Mapping irrigated areas in the Limpopo Province, South Africa

Cai, X.; Magidi, James; Nhamo, L.; Koppen, Barbara van

doi:10.5337/2017.205

Cited by 42 publications

(50 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Even less is known about irrigated agriculture. The DAFF national field boundary map gives an indication by assuming that horticulture/viticulture is irrigated, as in Figure 2a, in addition to center pivots as in Figure 2b, mapped by the International Water Management Institute (IWMI) (Cai et al 2017). However, this estimate suggests that irrigation primarily takes place in the former white areas.…”

Section: Rationalementioning

confidence: 99%

Smallholder irrigation schemes in the Limpopo Province, South Africa

Koppen¹,

Nhamo²,

Cai³

et al. 2017

Self Cite

View full text Add to dashboard Cite

A survey of 76 public smallholder irrigation schemes in the Limpopo Province was jointly conducted by the International Water Management Institute (IWMI), Department of Agriculture, Forestry and Fisheries (DAFF), South Africa, and the Limpopo Department of Agriculture and Rural Development (LDARD), as part of the ‘Revitalization of Smallholder Irrigation in South Africa’ project. About one-third of those schemes was fully utilized; one-third partially utilized; and one-third not utilized in the winter of 2015; however, no single socioeconomic, physical, agronomic and marketing variable could explain these differences in utilization. Sale, mostly for informal markets, appeared the most important goal. Dilapidated infrastructure was the most important constraint cited by the farmers. The study recommends ways to overcome the build-neglect-rebuild syndrome, and to learn lessons from informal irrigation, which covers an area three to four times as large as public irrigation schemes in the province

show abstract

Section: Rationalementioning

confidence: 99%

Smallholder irrigation schemes in the Limpopo Province, South Africa

Koppen¹,

Nhamo²,

Cai³

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…The amount of irrigation surfaces, which is of great importance to water resource management, is still unclear. Remote sensing technology leads to a new direction for mapping irrigated areas to better support water resources and agricultural development [7]. However, studies using remote sensing to map irrigated the metrics derived from the SAR backscatter time series, irrigated and non-irrigated fields can be separated.…”

Section: Introductionmentioning

confidence: 99%

Irrigation Mapping Using Sentinel-1 Time Series at Field Scale

et al. 2018

View full text Add to dashboard Cite

The recently launched Sentinel-1 satellite with a Synthetic Aperture Radar (SAR) sensor onboard offers a powerful tool for irrigation monitoring under various weather conditions, with high spatial and temporal resolution. This research discusses the potential of different metrics calculated from the Sentinel-1 time series for mapping irrigated fields. A methodology for irrigation mapping using SAR data is proposed. The study is performed using VV (vertical–vertical) and VH (vertical–horizontal) polarizations over an agricultural site in Urgell, Catalunya (Spain). With field segmentation information from SIGPAC (the Geographic Information System for Agricultural Parcels), the backscatter intensities are averaged within each field. From the Sentinel-1 time series for each field, the statistics and metrics, including the mean value, the variance of the signal, the correlation length, and the fractal dimension, are analyzed. With the Support Vector Machine (SVM), the classification of irrigated crops, irrigated trees, and non-irrigated fields is performed with the metrics vector. The results derived from the SVM are validated with ground truthing from SIGPAC over the whole study area, with a good overall accuracy of 81.08%. Random Forest (RF) machine classification is also tested in this study, which gives an accuracy of around 82.2% when setting the tree depth at three. The methodology is based only on SAR data, which makes it applicable to all areas, even with frequent cloud cover, but this method may be less robust when irrigation is less dominated to soil moisture change.

show abstract

“…Groundwater is the dominant source of safe water for rural populations and many expanding cities in EASE and SA (MacDonald et al, 2012); in drylands, groundwater is often the only perennial source of water. Although relatively underdeveloped to date, groundwater resources are being developed rapidly in Africa (Taylor et al, 2009;Calow et al, 2010;Villholth, 2013) and are featured prominently in national development plans, especially to satisfy the need for increased access to safe water and agricultural intensification under rapidly growing populations and economic development. Groundwater is especially important in Africa, where surface runoff efficiency is lower than elsewhere (McMahon et al, 1987) and drinking untreated surface water is associated with poor health (Hunter et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

The El Niño event of 2015–2016: climate anomalies and their impact on groundwater resources in East and Southern Africa

Kolusu

Shamsudduha

Todd

et al. 2019

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. The impact of climate variability on groundwater storage has received limited attention despite widespread dependence on groundwater as a resource for drinking water, agriculture and industry. Here, we assess the climate anomalies that occurred over Southern Africa (SA) and East Africa, south of the Equator (EASE), during the major El Niño event of 2015–2016, and their associated impacts on groundwater storage, across scales, through analysis of in situ groundwater piezometry and Gravity Recovery and Climate Experiment (GRACE) satellite data. At the continental scale, the El Niño of 2015–2016 was associated with a pronounced dipole of opposing rainfall anomalies over EASE and Southern Africa, north–south of ∼12∘ S, a characteristic pattern of the El Niño–Southern Oscillation (ENSO). Over Southern Africa the most intense drought event in the historical record occurred, based on an analysis of the cross-scale areal intensity of surface water balance anomalies (as represented by the standardised precipitation evapotranspiration index – SPEI), with an estimated return period of at least 200 years and a best estimate of 260 years. Climate risks are changing, and we estimate that anthropogenic warming only (ignoring changes to other climate variables, e.g. precipitation) has approximately doubled the risk of such an extreme SPEI drought event. These surface water balance deficits suppressed groundwater recharge, leading to a substantial groundwater storage decline indicated by both GRACE satellite and piezometric data in the Limpopo basin. Conversely, over EASE during the 2015–2016 El Niño event, anomalously wet conditions were observed with an estimated return period of ∼10 years, likely moderated by the absence of a strongly positive Indian Ocean zonal mode phase. The strong but not extreme rainy season increased groundwater storage, as shown by satellite GRACE data and rising groundwater levels observed at a site in central Tanzania. We note substantial uncertainties in separating groundwater from total water storage in GRACE data and show that consistency between GRACE and piezometric estimates of groundwater storage is apparent when spatial averaging scales are comparable. These results have implications for sustainable and climate-resilient groundwater resource management, including the potential for adaptive strategies, such as managed aquifer recharge during episodic recharge events.

show abstract

Mapping irrigated areas in the Limpopo Province, South Africa

Cited by 42 publications

References 3 publications

Smallholder irrigation schemes in the Limpopo Province, South Africa

Smallholder irrigation schemes in the Limpopo Province, South Africa

Irrigation Mapping Using Sentinel-1 Time Series at Field Scale

The El Niño event of 2015–2016: climate anomalies and their impact on groundwater resources in East and Southern Africa

Contact Info

Product

Resources

About