Irrigation Water Quality and Standards PDF

Course Title “Problematic Soils and their Managements” Topic “Irrigation water: quality and standard” Author: Dr. Manas Denre Assistant Professor Cum Junior Scientist Department of Soil Science & Agricultural Chemistry A...

Course Title “Problematic Soils and their Managements” Topic “Irrigation water: quality and standard” Author: Dr. Manas Denre Assistant Professor Cum Junior Scientist Department of Soil Science & Agricultural Chemistry Agriculture College Garhwa, Birsa Agricultural University, Ranchi-834006, Jharkhand  CONTENTS Particulars I Introduction II State wise irrigation facility of India III Irrigation water quality criteria IV Problems of agricultural crops and lands from using poor quality water V Factors affecting Suitability of Waters for Irrigation VI Management techniques of saline water VII How to utilize the saline waters in agriculture  I. INTRODUCTION “Water is life, no water no life” an immortal speech in all living being. When water is used for plant growth and development then become a question is it suitable for the cultivated land and crops? Because water is an impotent source for plant growth and development, through which plant nutrients become available form in the root zone and that is easily accumulated by the plant. But now a day due to climate change, over increasing population, industrialization and faulty of agricultural practices that had over exploit and polluted the water resources available to us. Poor quality water may affect irrigated crops by causing accumulate of salts in the root zone, loss of permeability of the soil due to excess sodium or calcium leaching, containing pathogens, specific ion toxicity and a group of other miscellaneous problems, which are directly toxic to plants or to those consuming them and often requires improvement before it is acceptable for a given use. Wastewater reuse is a common practice around the globe and is considered as an alternative water resource in a changing agricultural environment. Therefore, the aim of the present topic was to evaluate on “Irrigation water quality and standards, utilization of saline, effluent and sewage water in agriculture purpose”.  II. STATE WISE IRRIGATION TYPES AND CAPACITY Total crop area Groundwater irrigation Surface irrigation Irrigated area out of total Irrigated area out of State [million hectares (Mha)] crop area (Mha) crop area (Mha) crop area (Mha) Total crop area (%) Andhra Pradesh 14.3 2.5 2.7 4.9 34.27 Arunachal Pradesh 0.4 0.07 0.05 12.50 Assam 3.0 0.13 0.1 0.22 7.33 Bihar 6.4 2.2 1.3 3.5 54.69 Chhattisgarh 5.1 0.17 0.74 0.85 16.67 Goa 0.1 0.1 0.1 100.00 Gujarat 9.9 3.1 0.5 3.2 32.32 Haryana 3.6 1.99 1.32 3.26 90.56 Himachal Pradesh 1.0 0.02 0.09 0.11 11.00 Jammu & Kashmir 0.9 0.02 0.38 0.37 41.11 Jharkhand 3.2 0.11 0.13 0.24 7.50 Karnataka 12.2 1.43 1.33 2.38 19.51 Kerala 1.5 0.18 0.21 0.39 26.00 Madhya Pradesh 15.8 2.74 1.7 4.19 26.52 Maharashtra 19.8 3.12 1.03 3.36 16.97 Manipur 0.2 - 0.05 0.05 25.00 Meghalaya 0.3 - 0.06 0.06 20.00 Mizoram 0.1 - 0.01 0.01 10.00 Nagaland 1.1 - 0.1 0.07 6.36 Odisha 4.9 0.17 1.07 1.24 25.31 Punjab 4.0 3.06 0.94 3.96 99.00 Rajasthan 21.1 3.98 1.52 5.12 24.27 Sikkim 0.1 - 0.01 0.01 10.00 Tamil Nadu 6.5 1.61 1.43 2.66 40.92 Tripura 0.3 0.02 0.05 0.07 23.33 Uttar Pradesh 17.6 10.64 4.21 14.49 82.33 Uttarakhand 0.8 0.22 0.14 0.35 43.75 West Bengal 5.5 2.09 1.22 2.98 54.18 All India 159.6 39.43 22.48 58.13 36.42  Per cent (%) 10.00 20.00 30.00 40.00 70.00 80.00 90.00 50.00 60.00 100.00 0.00 Andhra Pradesh Arunachal Pradesh Assam Bihar Chhattisgarh Goa Gujarat Haryana Himachal Pradesh Jammu & Kashmir Jharkhand Karnataka Kerala Madhya Pradesh Maharashtra Name of States Manipur Meghalaya Mizoram Nagaland Odisha Punjab State wise irrigation area (%) out of total croped area Rajasthan Sikkim Tamil Nadu Tripura Uttar Pradesh Uttarakhand West Bengal  III. IRRIGATION WATER QUALITY CRITERIA The water quality is determined according to the purpose for which it will be used. For irrigation waters, the usual criteria include salinity, sodicity (sodium content), Organic matters, pH and element toxicities. Beside many important criteria is assessing water quality for other uses namely taste, colour, odour, turbidity, temperature, hardness, nutrient contents like nitrogen, phosphorus etc. and other pathogenic organisms are sometimes but not usually important for irrigation water. Soil Scientist uses the following categories to describe irrigation water effects on crop production and soil quality. 1. Organic matters (BOD) 2. Salinity hazard or total concentration of soluble salt 3. Sodium hazard- relative proportion of sodium to calcium and magnesium ions. 4. Salt index 5. pH- acidic or basic and alkalinity 6. Bicarbonate hazard 7. Boron concentration 8. Chloride concentration 9. Sulphate 10. Soluble sodium percentage (SSP) 11. Magnesium hazard 12. Nitrate concentration 13. Lithium 1. ORGANIC MATTERS Generally, biochemical oxygen demand (BOD) is used as an index for organic matter. Sludge and manure effluents have high BOD and COD (Chemical oxygen demand) and are undesirable for aquatic life (Fish, algae, plankton). Such water would also be more rapidly depleted of oxygen when added to poorly drained soils. In a high BOD environment, oxygen in water is consumed for decomposing organic matters to create an anaerobic state (Inadequate oxygen) and during the process of decomposition, oxides in the soil such as Fe3+, Mn5+, and SO42- consume oxygen to lower the oxidation-reduction potential. In the end, the generated iron, manganese and sulfide along with organic acids can disrupt the paddy rice to absorb nutrients. The maximum permissible limit of BOD and COD in irrigation water 2.0 and 4.0 mg L-1, respectively according to USPH standard. 2. SALINITY HAZARD Salinity hazard means total concentrations of soluble salts. Soluble salts, as referred to in soil science, are those inorganic chemicals that are more soluble than gypsum (CaSO4.2H2O), which has a solubility of about 0.241 gm per 100 ml of water at 250C. Common table salt (NaCl) has solubility nearly 150 times greater than gypsum (37.7 gm per 100 ml). Most soluble salt in saline water are composed of positively charged elements (cations) and negatively charged elements (anions). Cations include calcium, magnesium, sodium and potassium. Anions that will dissolve in water include carbonate, bicarbonate, nitrate, sulfate, chloride and boron Salinity has been deemed as the most important factor of agricultural water quality because high salinity in soil can create a hostile environment for the crop to absorb nutrients and provoke specific ion toxicity. The most influential water quality guide line on crop productivity is the water salinity hazard measured by total dissolved solids (TDS) or electrical conductivity (EC) and that expressed as dS m-1 (desiSiemens per meter). Higher the TDS or EC in water, also higher the salt hazard. Irrigation water is classified by its salt hazard. Guideline for electrical conductivity (EC) and total dissolved solids (TDS) of irrigation water. [Source: Bureau of Indian Standard, 1986] Water class EC Total Remarks (dS m-1 or mmhos cm-1) dissolved solids (TDS) (ppm) C1- Low salinity 26 Sometimes water pH also gives an indication of water salinity indirectly. An increase in pH reading of 1.0 or more, with change in the moisture content, form a low to high value has itself been found useful in some area for detecting alkali conditions in water. It is generally found that the higher the ESP, the higher is the water pH. A direct determination of exchangeable sodium in saline water by presence of sodium salt in equilibrium with exchangeable sodium in the water system. Exchangeable sodium percentage (ESP) = Total sodium (exchangeable + soluble) – Soluble sodium Where all the soluble ions ate expressed in meq L-1 General guidelines for sodium hazard of irrigation water based upon ESP value. [Sources: Ayers and Westcot (1994)] Water class ESP value Remarks Low sodium hazard 40 Unsatisfactory for most of the crops 4. SALT INDEX It is also used for predicting sodium hazard. It is the relation between Na+, Ca+ and CaCO3 present in irrigation water. Salt Index= (Total Na – 24.5) – [(Total Ca – Ca in + CaCO3) × 4.85] Where all quantity being expressed in ppm and all values of magnesium being reckoned as calcium. The salt index is negative (–24.5 to 0) for irrigation water high quality and many positive value of the salt index is harmful for irrigation purposes. The relative degree on both sides (negative and positive sides) depends on the magnitude of the “salt index” factor. 5. pH- ACID OR BASIC AND ALKALINITY The acidity and basicity of irrigation water is expressed as pH (7.0 basic). The normal pH range for irrigation water is form 6.5 to 8.4. High pH’s above 8.5 are often caused by high bicarbonate (HCO3–) and carbonate (CO32–) concentrations, known as alkalinity. High carbonates cause calcium and magnesium ions to form insoluble minerals leaving sodium as the dominant ion in solution. Excessive bicarbonate concentrates can also be problematic for drip or micro spray irrigation systems when calcite build up causes reduced flow rates through orifices or emitters. In these situations, correction by injection sulfuric or other acidic materials into the system may be required. 6. BICARBONATE HAZARD The bicarbonate (HCO3–) anion is an important in irrigation water as regards calcium and to a lesser degree also of magnesium as their carbonates (CO32–) in the soil. This brings about a change in the soluble sodium percentage (SSP) in the irrigation water and therefore, an increase of the sodium hazard. The residual sodium carbonate (RSC) is used to evaluate the quality of irrigation water and is expressed in meq L-1 (million equivalents per liter). RSC (meq L-1) = (CO32– + HCO3–) – (Ca2+ + Mg2+) Suggested limits for irrigation water based on residual sodium carbonate (RSC). [Source: Modified from Stevens (1994)] Water class RSC value (meq L-1) Water quality Very low 2.50 High risk. Generally unsuitable for irrigation, 7. BORON CONCENTRATION Boron is another element that is essential in low amounts, but toxic at higher concentrations. In fact, toxicity can occur on sensitive crops at concentrations less than 1.0 ppm. Colorado soils and irrigation waters contain enough B that additional B fertilizer is not required in most situations. Because B toxicity can occur at such low concentrations, an irrigation water analysis is advised for groundwater before applying additional B to crops. Permissible limits for boron in irrigation water in relation to different categories crops. [Source: Rowe and Abdel-Magid (1995)] Boron class Boron concentration (ppm) Remarks Sensitive crop Semi tolerant Tolerant crops crops Very low 3.75 8. SULFATE The sulfate ion is a major contributor to salinity in many of irrigation waters. As with boron, sulfate in irrigation water has fertility benefits and saline/waste irrigation water is often enough sulfate for maximum production for most crops. Exceptions are sandy fields with