M.A.M. Abdalla ; M.H. Abdel Salam and M.K.M.Abdel Razik( 2009). Performance Assessment Of Lateral Drains Under Non Uniform Irrigation Conditions In EgypEgypt. J. Of Appl. Sci., Vol. 24.No. 11, 2009, 286-300
Abstract: A field study was carried out on a clay soil provided with tile drainage system at the Eastern Nile Delta. The total area is approximately 250 feddan. Two drainage units were selected to achieve the objective from this study. The aim of the study is to evaluate the performance of lateral drains under non uniform irrigation conditions. The results revealed that the farm plots were never irrigated in one day and the maximum percentage irrigated in 10-days period was 98% of total area however, the average of irrigated area at the same period was only 51%. Also, both average and maximum irrigated area percentages for summer crops of maize and cotton are relatively greater than that of winter crops of wheat and berseem.
Concerning performance assessment of lateral drains, the modified method was applied where it uses only the readings of observation wells within the irrigated plots to determine the q-h relation, while only the q and h values measured two days after cession of the recharge that are used for entrance resistance calculations . The obtained results proved that the values calculated by the modified method for the hydraulic conductivity are practically almost equal to those resulting from the regular or traditional method. The results also showed that the values of q and h differ considerably, but their ratio does not change much. Regarding the head loss fraction and entrance resistance, data showed a significant difference was observed between the two methods although no trend could be distinguished. As for most of all tests, the assessment of the head loss fraction and entrance resistance by measuring and using daily observations of q and h showed moderate to large deviations from the ones of the modified method. The performance of the six lateral drains was assessed according to the entrance resistance and head losses fraction values using both the modified and regular methods.It could be recommended that the usage of this method can be applied on the areas of plot sizes smaller than lateral catchment ones, especially when drain testing is done for the verification of drainage design criteria q and h, and the determination of the use and type of envelope materials. In that case the head loss fraction and entrance resistance determinations are needed as well as their values appear to be significantly differences. Regarding the amounts of salt removal from lateral drains , the obtained results revealed that, the amounts of salt removal from lateral drains were relatively higher using the modified method (M) as compared with that obtained for the regular one (R). The amount of salts removal from lateral no.1 was much higher by about 23.1% for the modified method as compared with the regular one. The percentages were 6.5% ,4.1% ,14.3%,11.4% and14.7 % for laterals no. 2,3,4,5 and 6, respectively. The obtained results emphasized that, the good performance of the lateral drain no.3 showed a significant amount of salt removal (6.79-7.07 kg/fed./day), while the poor and very poor performance drains showed the lowest amounts of salts removal. Generally, it could be concluded that the amount of salt removal from lateral drains is an important parameter to assess the performance of lateral drains.
Keywords: (drain performance, uniformity of irrigation , entrance resistance, head losses fraction , drain assessment.)
