PCA driven watershed prioritization based on runoff modeling and drought severity assessment in parts of Koel river basin, Jharkhand (India)

Global warming influencing regional climate is playing a significant role in triggering the recurrent drought. The current study demonstrates a PCA (Principal Component Analysis) driven watershed prioritization in a part of Koel river basin by runoff computation during monsoon season along with assessment of Vegetation Health Index (VHI) derived from MODIS satellite data during the period from 2000 to 2017. Koel river catchment area of 7,261 sq km was divided into 82 sub-watersheds based on drainage networks derived from Survey of India (SOI) topographical map on scale 1: 50,000. High resolution satellite image of Sentinel-2 was used to prepare land use land cover map. Soil conservation service curve number method (SCS CN) was used to estimate runoff. Result obtained from runoff estimation of 82 sub watersheds shows high runoff (50 to 60% of rainfall) with 290,000 m3 total runoff volume in the upper and middle parts of the catchment dominated by agricultural/fallow and barren lands whereas low runoff was estimated (20 to 30%) with 29,467 m3 in the lower catchments where a large area is covered with forests. The value of satellite based VHI ranges between 23 to 53 with major parts of the area exhibiting values less than 30 reflecting poor vegetation health. Most of the sub-watersheds in parts of Ranchi, Lohardaga, Gumla and Khunti districts experienced high total runoff with poor vegetation health index reflecting more proneness to drought. Watershed prioritization was done based on correlation among four parameters viz., rainfall, drought zones, direct runoff and total runoff through PCA. Strong correlation between total runoff volume and drought areas was used for watershed prioritization which indicated 42 sub-watersheds (4,703 sq km) in the upper catchment required high prioritization. The outcomes of study would help proper planning of water resources and soil moisture management to overcome the recurrent drought conditions at watershed level.

PEMANTAUAN DAN MITIGASI TINGKAT POTENSI BENCANA KEKERINGAN DI KOTA DUMAI

Kekeringan lahan yang terjadi saat musim kemarau memberikan dampak buruk bagi vegetasi, salah satunya tanah Gambut sangat sensitif terhadap kenaikan suhu menimbulkan kebakaran hutan. Kota Dumai menjadi salah satu daerah yang sering mengalami kebakaran hutan dan lahan, efek terjadi kebakaran ini menjadikan lahan tersebut memiliki kualitas yang menurun meliputi fisika, kimia, dan adanya erosi tanah. Dalam tulisan ini, kami memantau adanya peningkatan dan penuruan dalam beberapa kategori kekeringan lahan. Adapun parameter yang digunakan seperti vegetation health index (VHI), vegetation condition index (VCI), dan temperature condition index (TCI) pada tahun 2013 dan tahun 2018. Hasil penelitian menjelaskan wilayah kekeringan mengalami kenaikan total selama periode pengamatan sebesar 23.119 hektar lahan, dengan kategori tanpa kekeringan terjadi penurunan seluas 23.119 ha, kemudian kategori kekeringan ringan terjadi peningkatan seluas19.510 ha, selanjutnya kategori kekeringan sedang terjadi peningkatan seluas 13.444 ha, lalu kategori kekeringan parah terjadi penurunan seluas 9.163 ha, dan kekeringan ekstrim mengalami penurunan seluas 672 ha. hal ini sejalan dengan terjadinya kenaikan pada suhu tahun 2013 mencapai 38 ºC kemudian mengalami peningkatan menjadi 47,53ºC di tahun 2018 yang sedang mengalami kebakaran hutan dan lahan

A Practical Satellite-Derived Vegetation Drought Index for Arid and Semi-Arid Grassland Drought Monitoring

In semi-arid pasture areas, drought may directly influence livestock production, cause economic losses, and accelerate the processes of desertification along with destructive human activities (i.e., overgrazing). The aim of this article is to analyze the disadvantages of several drought indices derived from remote sensing data and develop a new vegetation drought index (VDI) for monitoring of grassland drought with high temporal frequency (dekad) and fine spatial resolution (1 km). The site-based soil moisture data from the field campaign in 2014 and the fenced biomass values at nine sites from 2000 to 2015 were adopted for validation. The results indicate that the proposed VDI would better reflect the extent, severity, and changes of drought compared with single drought indices or the vegetation health index (VHI); specifically, the VDI is more closely related to site-based soil moisture, with R human increasing to approximately 0.07 compared with the VHI; and with normalized fenced biomass (NFB) values, with average R human increasing to approximately 0.11 compared with the VHI. However, the correlations between VHI and VDI with NFB values are relatively lower in desert steppe regions. Furthermore, regional drought-affected data (RDA) are used to ensure spatial consistency of the evaluation; the VDI map is in good agreement with the RDA map based on field measurements. The presented VDI shows reliable and stable drought monitoring ability, which will play an important role in the future drought monitoring of inland grassland.

Assessment of agricultural drought in Morocco based on a composite of the Vegetation Health Index (VHI) and Standardized Precipitation Evapotranspiration Index (SPEI)

According to IPCC, Morocco is a highly vulnerable country to extreme climate events, especially droughts; this will affect different socioeconomic sectors, mainly the agriculture sector. Droughts are controlled by the variability of precipitation and evapotranspiration but also not neglecting the effect of land surface conditions such as land surface temperature. In this present study, the remote sense observations MODIS Normalized Difference Vegetation Index (NDVI) and CMSAF Land Surface Temperature (LST) were used for calculating the Vegetation Health Index (VHI). The main advantage of remote sensing products is that they are reasonably efficient in terms of temporal and spatial coverage, and they are useful for the monitoring and assessment of drought in the near real-time. Furthermore, ERA5 Reanalysis-based SPEI is calculated. The goal of this study is to assess the spatial and temporal patterns of drought, this study offers the composite of SPEI and VHI drought monitoring obtained by plotting maps and graphs to show the monthly and annual variability of drought for the period 2000–2015 over the whole of Morocco. This monitoring can be used as a near real-time warning system in a changing climate.

Espaço-Temporalidade dos Focos de Calor na Região Metropolitana de Maceió

Resumo Este trabalho avaliou as queimadas e os incêndios na Região Metropolitana de Maceió (RMM) via dados de focos de calor (FC) disponíveis no BQueimadas para no período de 1999 a 2019. A série temporal de focos calor foi submetida às análises estatísticas descritivas e multivariadas (Análise de Agrupamento - AA) juntamente com Vegetation Health Index (VHI) aplicadas aos FC nos municípios da RMM. Com base no agrupamento hierárquico identificaram-se três grupos homogêneos (G1, G2 e G3) de FC e o município de Atalaia que não se agrupou (NA). Os Grupos G1 (145,5 ± 7,77 FC) e G2 (28,5 ± 44 FC) apresentaram similaridades quanto à sazonalidade dos FC. Enquanto o Grupo G3 (91 ± 7,07 FC) que inclui a capital Maceió, apresentou distribuição irregular espacialmente. Toda a variabilidade dos FC está associada às atividades agrícolas vigentes na RMM. Mas também, à negligência de ateio de material inflamável sobre a vegetação propicia aumento de incêndios e queimadas, principalmente na colheita da cana-de-açúcar.

Drought frequency characteristics of China, 1981-2019, based on the vegetation health index

Droughts—major natural disasters with a complex development and evolution process—cause enormous losses for society, especially in the agriculture sector. We analyzed the spatiotemporal evolution of drought frequency in China at grid level during 1981-2019 with the nonparametric Mann-Kendall trend method, using a high temporal resolution vegetation health index dataset at week-scale. Results suggest the that (1) after entering the 21st century, China’s drought-affected area has declined, with Northeast China being the least affected region and Northwest China being the most severely affected; (2) the spatial pattern of drought characteristics in China is polarized, and the frequency of droughts has generally declined, with the most prominent intensity and frequency observed in some urbanized and economically developed regions; and (3) although the changes to the drought characteristics and frequency in China provide a generally optimistic picture, drought intensity and frequency in some developed regions have increased significantly, and the future trend predictions for these areas are less positive. This study, focusing on the spatiotemporal characteristics and evolution of drought patterns, with the aim of raising awareness of drought disasters, can help mitigate and prevent the damage caused by droughts to society, and can provide a scientific basis for drought early-warning systems and risk management in China going forward.