Appraisal of Ground Water Quality and its Impact on Irrigated Soils in Khartoum State, Sudan

Abstract

A study was undertaken to appraise the quality and impact of
well waters on irrigated soils of fifty farms widely spread in Khartoum
State, Sudan. Water quality indicators and pertinent soil properties were
measured by standard procedures. The determinations were electrical
conductivity of water (ECw) and soil saturation extracts (ECe) and
soluble Na+ , K+ , Ca++ + Mg++ , Cl -
, HCO3- and SO4--
. Sodium adsorption
ratio (SAR), residual sodium carbonate (RSC), theoretical pH (pHc) and
Langeleir's saturation index (LSI) were computed. A questionnaire
including pertinent well and farm data and information was filled. ECw
ranged between 0.4 to 4.8 dS/m. According to the United States Salinity
Laboratory (USSL) classification system, 30% of the water samples lied
within the medium salinity class, 62% lied within the high salinity class
and 8% within the very high salinity class. In agreement with USSL,
highly significant linear correlations between ECw and total salt
concentration of water expressed in mmole+ /l or mg/l with 99%
accountability were found. Ninety-eight percent of the water samples
were non-sodic. Only one water sample gave a SAR value equal to 19.1
and the remaining waters had SAR ranging between 1.1 and 9.4. RSC was
negative for all water samples with the exception of two samples (4%)
that gave RSC values ≤ 0.6 and thus within the safe level. In general, LSI
data agreed with RSC data. The well waters were predominantly Ca-
Na/SO4 =Cl waters. The results showed that 70% of the top layer of the