Identification of droughts from monitored and modelled vegetation condition for improved water management in semi-arid areas

2020 ◽  
Author(s):  
Anita Bayer ◽  
Christine Mihalyfi-Dean ◽  
Robert Behling ◽  
Christof Lorenz ◽  
Saskia Foerster ◽  
...  
Keyword(s):  
Water Management ◽  
Remote Sensing ◽  
Water Availability ◽  
Standardized Precipitation Index ◽  
Integrated Analysis ◽  
Arid Areas ◽  
Large Variability ◽  
Vegetation Condition ◽  
Drought Indicators ◽  
Semi Arid

<p>Semi-arid areas suffer from small amounts and a large variability in rainfall combined with an increasing risk of droughts under climate change. These long and short-term changes in water availability directly affecting regional livelihoods are depicted in the condition of the rather sparse vegetation. In this study, seasonal and long-term trends in indicators of the vegetation condition related to water availability and droughts (NDVI vs. fAPAR, NPP, soil water content, excess water) are identified from remote sensing data (MODIS) and a process-based dynamic vegetation model (LPJ-GUESS) for at least two semi-arid river basins. Identified trends of both methods are compared and evaluated based on the underlying processes and related to knowledge of past drought events. Finally, we answer the question, which methods and indicators are suitable to identify changes in the vegetation condition preceding a drought and during drought phases considering the methods and indicators as above plus simple precipitation-based drought indicators (e.g. standardized precipitation index, SPI) and enhanced drought indicators applying multiple indicators theirselves (e.g. combined drought indicator, CDI). The study is imbedded in the SaWaM project (Seasonal Water Management for semi-arid areas) and contributes to improved water management in the project regions by the integrated analysis of remote sensing and ecosystem modelling results that are made available to regional stakeholders tasked with water management in an online tool .</p>

Remote sensing parameterization of land surface heat fluxes over arid and semi-arid areas

2003 ◽  
Vol 20 (4) ◽  
pp. 530-539 ◽  
Author(s):  
Ma Yaoming ◽  
Wang Jiemin ◽  
Huang Ronghui ◽  
Wei Guoan ◽  
Massimo Menenti ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Land Surface ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Arid Areas ◽  
Surface Heat Fluxes ◽  
Semi Arid ◽  
Land Surface Heat Fluxes

scholarly journals Assessment of actual evapotranspiration over a semi-arid heterogeneous land surface by means of coupled low resolution remote sensing data with energy balance model: comparison to extra Large Aperture Scintillometer measurements

2017 ◽  
Author(s):  
Sameh Saadi ◽  
Gilles Boulet ◽  
Malik Bahir ◽  
Aurore Brut ◽  
Bernard Mougenot ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Heat Flux ◽  
Water Stress ◽  
Latent Heat ◽  
Water Availability ◽  
Land Surface ◽  
Remote Sensing Data ◽  
Sparse Model ◽  
Sensing Data ◽  
Semi Arid

Abstract. In semi-arid areas, agricultural production is restricted by water availability; hence efficient agricultural water management is a major issue. The design of tools providing regional estimates of evapotranspiration (ET), one of the most relevant water balance fluxes, may help the sustainable management of water resources. Remote sensing provides periodic data about actual vegetation temporal dynamics (through the Normalized Difference Vegetation Index NDVI) and water availability under water stress (through the land surface temperature LST) which are crucial factors controlling ET. In this study, spatially distributed estimates of ET (or its energy equivalent, the latent heat fluxes LE) in the Kairouan plain (Central Tunisia) were computed by applying the Soil Plant Atmosphere and Remote Sensing Evapotraspiration (SPARSE) model fed by low resolution remote sensing data (Terra and Aqua MODIS). The work goal was to assess the operational use of the SPARSE model and the accuracy of the modelled i) sensible heat flux (H) and ii) daily ET over a heterogeneous semi-arid landscape with a complex land cover (i.e. trees, winter cereals, summer vegetables). The SPARSE's layer approach was run to compute instantaneous estimates of H and LE fluxes at the satellite overpass time. The good correspondence (R2 = 0.60 and 0.63 and RMSE = 57.89 W/m-2 and 53.85 W/m-2; for Terra and Aqua, respectively) between instantaneous H estimates and large aperture scintillometer (XLAS)'s H measurements along a pathlength of 4 km over the study area showed that the SPARSE model presents satisfactory accuracy. Results showed that, despite the fairly large scatter, the instantaneous LE can be suitably estimated at large scale (RMSE = 47.20 W/m-2 and 43.20 W/m-2; for Terra and Aqua, respectively and R2 = 0.55 for both satellites). Additionally, water stress was investigated by comparing modelled (SPARSE derived) to observed (XLAS derived) water stress values; we found that most points were located within a 0.2 confidence interval, thus the general tendencies are well reproduced. Even though extrapolation of instantaneous latent heat flux values to daily totals was less obvious, daily ET estimates are deemed acceptable.

Assessment of groundwater flow system for management of Stampriet Transboundary Aquifer System

2020 ◽  
Author(s):  
Irene Kinoti ◽  
Marc Leblanc ◽  
Albert Olioso ◽  
Maciek Lubczynski
Keyword(s):  
South Africa ◽  
Remote Sensing ◽  
Water Resources ◽  
Water Resource ◽  
Flow System ◽  
Arid Areas ◽  
Time Step ◽  
Transboundary Aquifer ◽  
Aquifer System ◽  
Semi Arid

<p>Groundwater is the main water resource in arid and semi-arid areas. Its evaluation in terms of recharge, discharge, flow system and change in storage is thus vital for management purposes. However, distributed numerical models which are considered as favourable tools for assessment of groundwater resources are often limited by availability of input data especially in arid and semi-arid areas in developing countries where monitoring networks are scarce. Moreover, in case of transboundary aquifers, political, institutional, cultural, socio-economic differences among countries make management of groundwater even more complex.</p><p>Remote sensing is a handy tool for monitoring water resources in data scarce areas. This study entails application of remote sensing data in developing a distributed integrated hydrological model for Stampriet Transboundary Aquifer System using MODFLOW-NWT coupled with the Unsaturated Zone Flow (UZF1) Package.</p><p>Stampriet Transboundary Aquifer is a multi-layered aquifer system shared between Namibia, Botswana and South Africa. The aquifer system consists of three aquifers, characterized by low transmissivity and low storage, intercalated by two aquitards. Conceptually, the physical processes taking place in this system are reasonably understood in Namibia and not as much in Botswana and South Africa. However, quantification of water resources and fluxes is still limited.</p><p>The aquifer system is mainly exploited in Namibia for socio-economic growth, where abstraction from storage has led to decline in local groundwater level. Water quality constraints have restrained its usage in South Africa, while in Botswana the potential for available resources is likely to be exploited, but there is not enough data for making firm decisions.</p><p>A numerical model has been set – up in transient conditions at daily time step and calibrated with groundwater levels as the state variables and satellite rainfall and potential evapotranspiration as the model driving forces. The calibrated model provides spatio-temporal water flux dynamics as well as water balances and hence an understanding of the groundwater-resource dynamics and replenishment. The results are compared to analysis of GRACE data to further constrain the model. This information is useful for proper management of the transboundary water resource as well as for policy making.</p>

scholarly journals Association between drought and agricultural productivity using remote sensing data: a case study of Gujarat state of India

2020 ◽  
Vol 11 (S1) ◽  
pp. 189-202 ◽  
Author(s):  
Koyel Sur ◽  
M. M. Lunagaria
Keyword(s):  
Remote Sensing ◽  
Crop Yield ◽  
Standardized Precipitation Index ◽  
Remote Sensing Data ◽  
Meteorological Drought ◽  
Drought Indices ◽  
Small Scale ◽  
Agricultural Crop ◽  
Vegetation Condition ◽  
Spatio Temporal

Abstract Drought is a complex hazard which directly affects the water balance of any region. It impacts agricultural, ecological and socioeconomical spheres. It is a global concern. The occurrence of drought is triggered by climatic phenomena which cannot be eliminated. However, its effect can be well managed if actual spatio-temporal information related to crop status influenced by drought is available to decision-makers. This study attempted to assess the efficiency of remote sensing products from space sensors for monitoring the spatio-temporal status of meteorological drought in conjunction with impact on vegetation condition and crop yield. Time series (2000–2019) datasets of the Tropical Rainfall Measuring Mission (TRMM) were used to compute Standardized Precipitation Index (SPI) and MODIS (MODerate resolution Imaging Spectroradiometer) was used to compute Vegetation Condition Index (VCI). Association between SPI and VCI was explored. YAI was calculated from the statistical data records. Final observations are that the agricultural crop yield changed as per the climate variability specific to location. The study indicates drought indices derived from remote sensing give a synoptic view because of the course resolution of the satellite images. It does not reveal the precise relationship to the small-scale crop yield. Remote sensing can be an effective way to monitor and understand the dynamics of the drought and agriculture pattern over any region.

scholarly journals Remote Sensing for Biocultural Heritage Preservation in an African Semi-Arid Region: A Case Study of Indigenous Wells in Northern Kenya and Southern Ethiopia

2022 ◽  
Vol 14 (2) ◽  
pp. 314
Author(s):  
Pamela Ochungo ◽  
Nadia Khalaf ◽  
Stefania Merlo ◽  
Alemseged Beldados ◽  
Freda Nkirote M’Mbogori ◽  
...  
Keyword(s):  
Water Management ◽  
Remote Sensing ◽  
Land Cover ◽  
Diversity Index ◽  
Management Systems ◽  
Southern Ethiopia ◽  
Northern Kenya ◽  
Landscape Degradation ◽  
Biocultural Heritage ◽  
Semi Arid

The region of Southern Ethiopia (Borana) and Northern Kenya (Marsabit) is characterised by erratic rainfall, limited surface water, aridity, and frequent droughts. An important adaptive response to these conditions, of uncertain antiquity, has been the hand-excavation of a sequence of deep wells at key locations often along seasonal riverbeds and valley bottoms where subterranean aquifers can be tapped. Sophisticated indigenous water management systems have developed to ensure equitable access to these critical water resources, and these are part of well-defined customary institutional leadership structures that govern the community giving rise to a distinctive form of biocultural heritage. These systems, and the wells themselves, are increasingly under threat, however, from climate change, demographic growth, and socio-economic development. To contribute to an assessment of the scale, distribution and intensity of these threats, this study aimed to evaluate the land-use land-cover (LULC) and precipitation changes in this semi-arid to arid landscape and their association with, and impact on, the preservation of traditional wells. Multitemporal Landsat 5, 7 and 8 satellite imagery covering the period 1990 to 2020, analysed at a temporal resolution of 10 years, was classified using supervised classification via the Random Forest machine learning method to extract the following classes: bare land, grassland, shrub land, open forest, closed forest, croplands, settlement and waterbodies. Change detection was then applied to identify and quantify changes through time and landscape degradation indices were generated using the Shannon Diversity Index fragmentation index within a 15 km buffer of each well cluster. The results indicated that land cover change was mostly driven by increasing anthropogenic changes with resultant reduction in natural land cover classes. Furthermore, increased fragmentation has occurred within most of the selected buffer distances of the well clusters. The main drivers of change that have directly or indirectly impacted land degradation and the preservation of indigenous water management systems were identified through an analysis of land cover changes in the last 30 years, supporting insights from previous focused group discussions with communities in Kenya and Ethiopia. Our approach showed that remote sensing methods can be used for the spatially explicit mapping of landscape structure around the wells, and ultimately towards assessment of the preservation status of the indigenous wells.

Water Management of Irrigated Cabernet Sauvignon Grapevines in Semi-Arid Areas

2017 ◽  
Vol 68 (4) ◽  
pp. 458-467 ◽  
Author(s):  
James E. Ayars ◽  
Isabel Abrisqueta ◽  
Christopher Parry ◽  
Anji Perry ◽  
Andrew J. McElrone
Keyword(s):  
Water Management ◽  
Cabernet Sauvignon ◽  
Arid Areas ◽  
Semi Arid
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