Python数据分析实例，利用Pandas建立流域三层蒸发和蓄满产流模型

根据水量平衡方程推求土壤含水量

if i ==1:
	df["WU"][i] = WUM
	df["WL"][i] = WLM
	df["WD"][i] = WDM
              
else:
	dw=df["PE"][i-1]-df['R'][i-1]
	df["WU"][i] = df["WU"][i-1]+dw
	df["WL"][i] = df["WL"][i-1]
	df["WD"][i] = df["WD"][i-1]
	if df["WU"][i] < 0:
		df["WL"][i] = df["WL"][i-1]+df["WU"][i]
		df["WU"][i] = 0
		df["WD"][i] = df["WD"][i-1]
		if df["WL"][i] < 0:
			df["WD"][i] = df["WD"][i-1]+df["WL"][i]
			df["WL"][i] = 0
			df["WU"][i] = 0
			if df["WD"][i]<0:
				df["WL"][i] = 0
				df["WU"][i] = 0
				df["WD"][i] = 0
                                
	if df["WU"][i] > WUM:
		df["WL"][i] = df["WU"][i]-WUM+df["WL"][i-1]
		df["WU"][i] = WUM
		df["WD"][i] = df["WD"][i-1]
		if df["WL"][i] > WLM:
			df["WD"][i] = df["WL"][i]-WLM+df["WD"][i-1]
			df["WL"][i] = WLM
			df["WU"][i] = WUM
			if df["WD"][i] > WDM:
				df["WL"][i] = WLM
				df["WU"][i] = WUM
				df["WD"][i] = WDM

土壤三层蒸发模型，EU,EL,ED的计算

if df["WU"][i]+df["P"][i] >= df["EP"][i]:
	df["EU"][i]=df["EP"][i]
	df["EL"][i]=0
	df["ED"][i]=0
if df["WU"][i]+df["P"][i] < df["EP"][i] and df["WL"][i] >= C*WLM:
	df["EU"][i]=df["WU"][i]+df["P"][i]
	df["EL"][i]