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Suitability of surface water for irrigation in the Maffragh basin, North-East of Algeria

Boubguira Selwa, Zouini Derradji, Lamine Sayad, Dali Nawel

Journal of Water and Land Development

2021

no. 48

94--98

Water quality is an environmental priority for irrigation in rainfed agriculture. Recently, water quality has been affected by the uncontrolled disposal of wastewater, the use of chemical fertilizers in agriculture and, most significantly, by the excessive exploitation of water resources during the low season. The basin of the Maffragh in the Algerian north-east real is fed by two main rivers: Wadi El Kebir East and Bounnamoussa. From its source, the stream is continually contaminated with domestic and agricultural discharges through the tributaries causing a significant deterioration in water quality. In order to know the current state of water quality in the Maffragh basin and to determine its suitability for irrigation without any prior treatment, research has been conducted in the two streams at representative sampling points in catchment areas used for irrigating crops. To assess the quality of water and detectable compounds monitoring, laboratory methods are used. The various volumetric and colorimetric assays were carried out according to Jean Rodier. Organic parameters such as nitrites, ammonium and phosphates, were measured using a UV/VIS 6705 JENWAY spectrophotometer, at wavelengths of 543 nm, 630 nm and 880 nm respectively for nitrites, ammonium and phosphates. The BOD5 and COD parameter was measured using a DIN EN 1899-1-H51 spectrophotometer and DIN ISO15705: 2002 spectrophotometer. The performed analyses on conductivity shows oscillating values ranging between 425 and 495 μS∙cm–1 for January 2018, while for the low water level of July 2018 the conductivity varies between 433 and 796 μS∙cm–1; this parameter is determinant for water quality assessment and its use for irrigation. Beside the conductivity test, the Riverside–Wilcox diagram was applied, to combine conductivity and sodium absorption rate (SAR). The obtained results of the two seasons show satisfactory results in the applicability of the water to irrigate in the basin.

Statistical assessment of rainfall variability and trends in northeastern Algeria

Merniz Noureddine, Tahar Ali, Benmehaia Amine M.

Journal of Water and Land Development

2019

no. 40

87--96

In the present study, time series for annual, monthly rainfall and number of rainy days per year were analysed to quantify spatial variability and temporal trends for 22 rainfall stations distributed in northeastern Algeria for the period 1978– 2010. The Mann–Kendall test and the Sen’s slope estimator were applied to assess the significance and magnitude of the trend. The results showed that precipitation decreases spatially from North to South and from East to West. The application of the Mann–Kendall test (for 0.05% threshold) to the time series data showed that for annual precipitation, no station showed statistically significant trends, unlike the number of rainy days, where there was a significant negative trend in four stations (Jijel, Constantine, Oum El Bouaghi and Tébessa). For the monthly time series, significant positive trends were observed during the months of September in the coastal stations and July for the plateaus and southern Saharan Atlas stations, while significant negative trends were recorded during the months of February and March for the stations of the extreme East in the study area. These results revealed that for the period analysed, there was no significant climate change in northeastern Algeria but there is a seasonal delay having important agroecological implications.

W przedstawionych badaniach analizowano serie rocznych i miesięcznych opadów oraz liczbę dni z deszczem w ciągu roku celem ustalenia przestrzennej zmienności i czasowych trendów w latach 1978–2010 dla 22 stacji pomiarowych rozmieszczonych w północnowschodniej Algierii. Wykorzystano test Manna–Kendalla i estymator Sena do oceny istotności i rozmiaru trendu. Wyniki dowodzą, że opady malały z północy na południe i ze wschodu na zachód. Zastosowanie testu Manna–Kendalla (p < 0,05) do serii danych pomiarowych nie wykazały w żadnej stacji statystycznie istotnych trendów dla rocznych opadów w przeciwieństwie do liczby dni z opadem, które cechował istotny negatywny trend w czterech stacjach pomiarowych (Jijel, Constantine, Oum El Bouaghi i Tébessa). Analiza serii miesięcznych opadów dowiodła występowania dodatniego trendu w odniesieniu do sierpnia w stacjach na wybrzeżu i w odniesieniu do lipca w stacjach na płaskowyżach i w południowym Atlasie Saharyjskim. Istotny trend ujemny uzyskano w przypadku lutego i marca w stacjach na wschodzie badanego obszaru. Wyniki dowodzą, że w analizowanym okresie nie stwierdzono istotnych zmian klimatu w północnowschodniej Algierii, z wyjątkiem sezonowych opóźnień, które wywołują ważne skutki agro-ekologiczne.