Accurate identification of drought events, supported by reliable and consistent spatiotemporal da... more Accurate identification of drought events, supported by reliable and consistent spatiotemporal data, is essential for the development of efficient management and mitigation plans. The objectives of this study are twofold. First, we evaluate a wide range of global precipitation and potential evapotranspiration (PET) products versus in-situ observations for the period of 2001–2016 to identify the best-performing ones for drought assessment. Second, we assess the drought impact on groundwater storage and agricultural yield using Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI). The impact of drought on groundwater and agricultural yield was examined by investigating the association between SPI and SPEI with the Gravity Recovery and Climate Experiment (GRACE) satellite data, total crop production (CP), and total wheat production (WP). The results showed that the most severe and prolonged droughts occurred primarily in northwest highlands, northeastern regions, and southern regions, with SPI values indicating more intense drought events than SPEI values. While the SPEI index was found to be more suitable for assessing long-term drought severity, the SPI index was more sensitive to short-term precipitation deficits. Groundwater storage changes were found to be highly associated with SPEI/SPI at longer time scales. Furthermore, the results indicate that the strongest association between drought and yield loss occurs at the 9-month time scale. However, SPI exhibits a higher association with crop yield compared to SPEI. These findings can contribute to the development of drought management and response strategies.
In this study, a methodology was developed for AGR assessment, including site selection, non-stat... more In this study, a methodology was developed for AGR assessment, including site selection, non-stationary kriging, numerical modeling, and the long-term supply and demand sustainability. To achieve this, spatial variations maps of effective parameters were prepared using kriging techniques along with the Fuzzy logic method and GIS analytical functions for AGR site selection. To estimate how AGR is changing the water balance in the region, the Soil Water Assessment Tools (SWAT) hydrological model was coupled with an in house 2-D finite difference groundwater model. Based on the SWAT model results, by applying AGR, infiltration increased dramatically from 101 to 146 mm. In order to improve the model’s accuracy, transmissivity was regionalized through non-stationary kriging by splitting the region into sub-regions where the characteristics of each variogram are different. By using non-stationary kriging, the statistic R2 from single variogram to multiple variograms increased from 0.27 to 0.95, and the groundwater level was improved by 15%. Furthermore, for evaluating the sustainability of water resources, an index called Planning for Sustainable Index (PSUI) was utilized to measure AGR effects. PSUI, after applying AGR without changing in water withdrawal, was increased from 0.11 to 0.17 during 27-years time horizon. The case study is the aquifer in Qorveh Dehgolan sub-basin in Kordestan province, Iran. The results indicate that by applying AGR to the region, the rate of groundwater level reduction would decrease significantly for about 30%. However, for preventing the groundwater depletion, AGR should be accompanied by 50% reduction in withdrawals/pumping. The results show the significant value of utilizing a platform to assess the attributes and benefits of AGR. The proposed algorithm can be used for other geographical settings.
Extreme precipitation events such as floods and droughts have occurred with higher frequency over... more Extreme precipitation events such as floods and droughts have occurred with higher frequency over the recent decades as a result of the climate change and anthropogenic activities. To understand and mitigate such events, it is crucial to investigate their spatio-temporal variations globally or regionally. Global precipitation products provide an alternative way to the in situ observations over such a region. In this study, we have evaluated the performance of the latest version of the Global Precipitation Measurement-Integrated Multi-satellitE Retrievals (GPM-IMERGV6.0 Final Run (GPM-IMERGF)). To this end, we have employed ten most common extreme precipitation indices, including maximum indices (Rx1day, Rx5day, CDD, and CWD), percentile indices (R95pTOT and R99pTOT), and absolute threshold indices (R10mm, R20mm, SDII, and PRCPTOT). Overall, the spatial distribution results for error metrics showed that the highest and lowest accuracy for GPM-IMERGF were reported for the absolute thr...
Accurate identification of drought events, supported by reliable and consistent spatiotemporal da... more Accurate identification of drought events, supported by reliable and consistent spatiotemporal data, is essential for the development of efficient management and mitigation plans. The objectives of this study are twofold. First, we evaluate a wide range of global precipitation and potential evapotranspiration (PET) products versus in-situ observations for the period of 2001–2016 to identify the best-performing ones for drought assessment. Second, we assess the drought impact on groundwater storage and agricultural yield using Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI). The impact of drought on groundwater and agricultural yield was examined by investigating the association between SPI and SPEI with the Gravity Recovery and Climate Experiment (GRACE) satellite data, total crop production (CP), and total wheat production (WP). The results showed that the most severe and prolonged droughts occurred primarily in northwest highlands, northeastern regions, and southern regions, with SPI values indicating more intense drought events than SPEI values. While the SPEI index was found to be more suitable for assessing long-term drought severity, the SPI index was more sensitive to short-term precipitation deficits. Groundwater storage changes were found to be highly associated with SPEI/SPI at longer time scales. Furthermore, the results indicate that the strongest association between drought and yield loss occurs at the 9-month time scale. However, SPI exhibits a higher association with crop yield compared to SPEI. These findings can contribute to the development of drought management and response strategies.
In this study, a methodology was developed for AGR assessment, including site selection, non-stat... more In this study, a methodology was developed for AGR assessment, including site selection, non-stationary kriging, numerical modeling, and the long-term supply and demand sustainability. To achieve this, spatial variations maps of effective parameters were prepared using kriging techniques along with the Fuzzy logic method and GIS analytical functions for AGR site selection. To estimate how AGR is changing the water balance in the region, the Soil Water Assessment Tools (SWAT) hydrological model was coupled with an in house 2-D finite difference groundwater model. Based on the SWAT model results, by applying AGR, infiltration increased dramatically from 101 to 146 mm. In order to improve the model’s accuracy, transmissivity was regionalized through non-stationary kriging by splitting the region into sub-regions where the characteristics of each variogram are different. By using non-stationary kriging, the statistic R2 from single variogram to multiple variograms increased from 0.27 to 0.95, and the groundwater level was improved by 15%. Furthermore, for evaluating the sustainability of water resources, an index called Planning for Sustainable Index (PSUI) was utilized to measure AGR effects. PSUI, after applying AGR without changing in water withdrawal, was increased from 0.11 to 0.17 during 27-years time horizon. The case study is the aquifer in Qorveh Dehgolan sub-basin in Kordestan province, Iran. The results indicate that by applying AGR to the region, the rate of groundwater level reduction would decrease significantly for about 30%. However, for preventing the groundwater depletion, AGR should be accompanied by 50% reduction in withdrawals/pumping. The results show the significant value of utilizing a platform to assess the attributes and benefits of AGR. The proposed algorithm can be used for other geographical settings.
Extreme precipitation events such as floods and droughts have occurred with higher frequency over... more Extreme precipitation events such as floods and droughts have occurred with higher frequency over the recent decades as a result of the climate change and anthropogenic activities. To understand and mitigate such events, it is crucial to investigate their spatio-temporal variations globally or regionally. Global precipitation products provide an alternative way to the in situ observations over such a region. In this study, we have evaluated the performance of the latest version of the Global Precipitation Measurement-Integrated Multi-satellitE Retrievals (GPM-IMERGV6.0 Final Run (GPM-IMERGF)). To this end, we have employed ten most common extreme precipitation indices, including maximum indices (Rx1day, Rx5day, CDD, and CWD), percentile indices (R95pTOT and R99pTOT), and absolute threshold indices (R10mm, R20mm, SDII, and PRCPTOT). Overall, the spatial distribution results for error metrics showed that the highest and lowest accuracy for GPM-IMERGF were reported for the absolute thr...
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Papers by javad teymoori